diff --git a/build.sbt b/build.sbt
index 37aee634..68b11ccc 100644
--- a/build.sbt
+++ b/build.sbt
@@ -141,6 +141,7 @@ val common = project.in(file("modules/common")).
       Dependencies.fs2 ++
       Dependencies.circe ++
       Dependencies.loggingApi ++
+      Dependencies.calevCore ++
       Dependencies.pureconfig.map(_ % "optional")
   )
 
diff --git a/modules/common/src/main/scala/docspell/common/Timestamp.scala b/modules/common/src/main/scala/docspell/common/Timestamp.scala
index bd496efb..d5298c56 100644
--- a/modules/common/src/main/scala/docspell/common/Timestamp.scala
+++ b/modules/common/src/main/scala/docspell/common/Timestamp.scala
@@ -16,6 +16,9 @@ case class Timestamp(value: Instant) {
   def minus(d: Duration): Timestamp =
     Timestamp(value.minusNanos(d.nanos))
 
+  def - (d: Duration): Timestamp =
+    minus(d)
+
   def minusHours(n: Long): Timestamp =
     Timestamp(value.minusSeconds(n * 60 * 60))
 
@@ -31,6 +34,9 @@ case class Timestamp(value: Instant) {
   def atUTC: ZonedDateTime = atZone(Timestamp.UTC)
 
   def asString: String = value.toString
+
+  def < (other: Timestamp): Boolean =
+    this.value.isBefore(other.value)
 }
 
 object Timestamp {
diff --git a/modules/common/src/main/scala/docspell/common/pureconfig/Implicits.scala b/modules/common/src/main/scala/docspell/common/pureconfig/Implicits.scala
index 7fc880ab..ceee5629 100644
--- a/modules/common/src/main/scala/docspell/common/pureconfig/Implicits.scala
+++ b/modules/common/src/main/scala/docspell/common/pureconfig/Implicits.scala
@@ -4,6 +4,7 @@ import docspell.common._
 import _root_.pureconfig._
 import _root_.pureconfig.error.{CannotConvert, FailureReason}
 import scodec.bits.ByteVector
+import com.github.eikek.calev.CalEvent
 
 import scala.reflect.ClassTag
 
@@ -31,6 +32,10 @@ object Implicits {
       else ByteVector.encodeUtf8(str).left.map(ex => s"Invalid utf8 string: ${ex.getMessage}")
     })
 
+  implicit val caleventReader: ConfigReader[CalEvent] =
+    ConfigReader[String].emap(reason(CalEvent.parse))
+
+
   def reason[A: ClassTag](f: String => Either[String, A]): String => Either[FailureReason, A] =
     in =>
       f(in).left.map(str => CannotConvert(in, implicitly[ClassTag[A]].runtimeClass.toString, str))
diff --git a/modules/joex/src/main/resources/reference.conf b/modules/joex/src/main/resources/reference.conf
index ba056a83..461f6fce 100644
--- a/modules/joex/src/main/resources/reference.conf
+++ b/modules/joex/src/main/resources/reference.conf
@@ -77,6 +77,21 @@ docspell.joex {
     wakeup-period = "10 minutes"
   }
 
+  # Docspell uses periodic house keeping tasks, like cleaning expired
+  # invites, that can be configured here.
+  house-keeping {
+
+    # When the house keeping task executes. Default is every 4 hours.
+    schedule = "*-*-* 0/4:00:00"
+
+    # This task removes invitation keys that have been created but not
+    # used. The timespan here must be greater than the `invite-time'
+    # setting in the rest server config file.
+    cleanup-invites = {
+      older-than = "30 days"
+    }
+  }
+
   # Configuration of text extraction
   extraction {
     # For PDF files it is first tried to read the text parts of the
diff --git a/modules/joex/src/main/scala/docspell/joex/Config.scala b/modules/joex/src/main/scala/docspell/joex/Config.scala
index a3f18d60..1d678766 100644
--- a/modules/joex/src/main/scala/docspell/joex/Config.scala
+++ b/modules/joex/src/main/scala/docspell/joex/Config.scala
@@ -5,6 +5,7 @@ import docspell.joex.scheduler.{PeriodicSchedulerConfig, SchedulerConfig}
 import docspell.store.JdbcConfig
 import docspell.convert.ConvertConfig
 import docspell.extract.ExtractConfig
+import docspell.joex.hk.HouseKeepingConfig
 
 case class Config(
     appId: Ident,
@@ -13,6 +14,7 @@ case class Config(
     jdbc: JdbcConfig,
     scheduler: SchedulerConfig,
     periodicScheduler: PeriodicSchedulerConfig,
+    houseKeeping: HouseKeepingConfig,
     extraction: ExtractConfig,
     convert: ConvertConfig
 )
diff --git a/modules/joex/src/main/scala/docspell/joex/JoexAppImpl.scala b/modules/joex/src/main/scala/docspell/joex/JoexAppImpl.scala
index 45045137..c16a1a33 100644
--- a/modules/joex/src/main/scala/docspell/joex/JoexAppImpl.scala
+++ b/modules/joex/src/main/scala/docspell/joex/JoexAppImpl.scala
@@ -3,9 +3,10 @@ package docspell.joex
 import cats.implicits._
 import cats.effect._
 import docspell.common.{Ident, NodeType, ProcessItemArgs}
-import docspell.joex.background._
+import docspell.joex.hk._
 import docspell.joex.process.ItemHandler
 import docspell.joex.scheduler._
+import docspell.joexapi.client.JoexClient
 import docspell.store.Store
 import docspell.store.queue._
 import docspell.store.ops.ONode
@@ -18,6 +19,7 @@ final class JoexAppImpl[F[_]: ConcurrentEffect: ContextShift: Timer](
     cfg: Config,
     nodeOps: ONode[F],
     store: Store[F],
+    pstore: PeriodicTaskStore[F],
     termSignal: SignallingRef[F, Boolean],
     val scheduler: Scheduler[F],
     val periodicScheduler: PeriodicScheduler[F]
@@ -27,6 +29,7 @@ final class JoexAppImpl[F[_]: ConcurrentEffect: ContextShift: Timer](
     val run  = scheduler.start.compile.drain
     val prun = periodicScheduler.start.compile.drain
     for {
+      _ <- HouseKeepingTask.submit(pstore, cfg.houseKeeping.schedule)
       _ <- ConcurrentEffect[F].start(run)
       _ <- ConcurrentEffect[F].start(prun)
       _ <- scheduler.periodicAwake
@@ -52,14 +55,15 @@ object JoexAppImpl {
       cfg: Config,
       termSignal: SignallingRef[F, Boolean],
       connectEC: ExecutionContext,
+      clientEC: ExecutionContext,
       blocker: Blocker
   ): Resource[F, JoexApp[F]] =
     for {
+      client <- JoexClient.resource(clientEC)
       store   <- Store.create(cfg.jdbc, connectEC, blocker)
       queue   <- JobQueue(store)
       pstore  <- PeriodicTaskStore.create(store)
       nodeOps <- ONode(store)
-      psch    <- PeriodicScheduler.create(cfg.periodicScheduler, queue, pstore, Timer[F])
       sch <- SchedulerBuilder(cfg.scheduler, blocker, store)
         .withQueue(queue)
         .withTask(
@@ -71,13 +75,14 @@ object JoexAppImpl {
         )
         .withTask(
           JobTask.json(
-            PeriodicTask.taskName,
-            PeriodicTask[F](cfg),
-            PeriodicTask.onCancel[F]
+            HouseKeepingTask.taskName,
+            HouseKeepingTask[F](cfg),
+            HouseKeepingTask.onCancel[F]
           )
         )
         .resource
-      app = new JoexAppImpl(cfg, nodeOps, store, termSignal, sch, psch)
+      psch    <- PeriodicScheduler.create(cfg.periodicScheduler, sch, queue, pstore, client, Timer[F])
+      app = new JoexAppImpl(cfg, nodeOps, store, pstore, termSignal, sch, psch)
       appR <- Resource.make(app.init.map(_ => app))(_.shutdown)
     } yield appR
 }
diff --git a/modules/joex/src/main/scala/docspell/joex/JoexServer.scala b/modules/joex/src/main/scala/docspell/joex/JoexServer.scala
index 00919923..c5966549 100644
--- a/modules/joex/src/main/scala/docspell/joex/JoexServer.scala
+++ b/modules/joex/src/main/scala/docspell/joex/JoexServer.scala
@@ -24,13 +24,14 @@ object JoexServer {
   def stream[F[_]: ConcurrentEffect: ContextShift](
       cfg: Config,
       connectEC: ExecutionContext,
+      clientEC: ExecutionContext,
       blocker: Blocker
   )(implicit T: Timer[F]): Stream[F, Nothing] = {
 
     val app = for {
       signal   <- Resource.liftF(SignallingRef[F, Boolean](false))
       exitCode <- Resource.liftF(Ref[F].of(ExitCode.Success))
-      joexApp  <- JoexAppImpl.create[F](cfg, signal, connectEC, blocker)
+      joexApp  <- JoexAppImpl.create[F](cfg, signal, connectEC, clientEC, blocker)
 
       httpApp = Router(
         "/api/info" -> InfoRoutes(),
diff --git a/modules/joex/src/main/scala/docspell/joex/Main.scala b/modules/joex/src/main/scala/docspell/joex/Main.scala
index a800acdb..4c1f7319 100644
--- a/modules/joex/src/main/scala/docspell/joex/Main.scala
+++ b/modules/joex/src/main/scala/docspell/joex/Main.scala
@@ -13,10 +13,10 @@ import org.log4s._
 object Main extends IOApp {
   private[this] val logger = getLogger
 
-  val blockingEc: ExecutionContext = ExecutionContext.fromExecutor(
+  val blockingEC: ExecutionContext = ExecutionContext.fromExecutor(
     Executors.newCachedThreadPool(ThreadFactories.ofName("docspell-joex-blocking"))
   )
-  val blocker = Blocker.liftExecutionContext(blockingEc)
+  val blocker = Blocker.liftExecutionContext(blockingEC)
   val connectEC: ExecutionContext = ExecutionContext.fromExecutorService(
     Executors.newFixedThreadPool(5, ThreadFactories.ofName("docspell-joex-dbconnect"))
   )
@@ -52,6 +52,6 @@ object Main extends IOApp {
       cfg.baseUrl
     )
     logger.info(s"\n${banner.render("***>")}")
-    JoexServer.stream[IO](cfg, connectEC, blocker).compile.drain.as(ExitCode.Success)
+    JoexServer.stream[IO](cfg, connectEC, blockingEC, blocker).compile.drain.as(ExitCode.Success)
   }
 }
diff --git a/modules/joex/src/main/scala/docspell/joex/hk/CleanupInvitesTask.scala b/modules/joex/src/main/scala/docspell/joex/hk/CleanupInvitesTask.scala
new file mode 100644
index 00000000..592a80b8
--- /dev/null
+++ b/modules/joex/src/main/scala/docspell/joex/hk/CleanupInvitesTask.scala
@@ -0,0 +1,24 @@
+package docspell.joex.hk
+
+import cats.implicits._
+import cats.effect._
+
+import docspell.common._
+import docspell.joex.Config
+import docspell.joex.scheduler.Task
+import docspell.store.records._
+
+object CleanupInvitesTask {
+
+  def apply[F[_]: Sync: ContextShift](cfg: Config): Task[F, Unit, Unit] =
+    Task { ctx =>
+      val threshold = cfg.houseKeeping.cleanupInvites.olderThan
+      for {
+        now <- Timestamp.current[F]
+        ts = now - threshold
+        _   <- ctx.logger.info(s"Cleanup invitations older than $ts")
+        n   <- ctx.store.transact(RInvitation.deleteOlderThan(ts))
+        _   <- ctx.logger.info(s"Removed $n invitations")
+      } yield ()
+    }
+}
diff --git a/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingConfig.scala b/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingConfig.scala
new file mode 100644
index 00000000..bf826db2
--- /dev/null
+++ b/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingConfig.scala
@@ -0,0 +1,17 @@
+package docspell.joex.hk
+
+import com.github.eikek.calev.CalEvent
+import docspell.common._
+
+import HouseKeepingConfig._
+
+case class HouseKeepingConfig(
+  schedule: CalEvent,
+  cleanupInvites: CleanupInvites
+)
+
+object HouseKeepingConfig {
+
+  case class CleanupInvites(olderThan: Duration)
+
+}
diff --git a/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingTask.scala b/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingTask.scala
new file mode 100644
index 00000000..07339baf
--- /dev/null
+++ b/modules/joex/src/main/scala/docspell/joex/hk/HouseKeepingTask.scala
@@ -0,0 +1,50 @@
+package docspell.joex.hk
+
+import cats.implicits._
+import cats.effect._
+import com.github.eikek.calev._
+
+import docspell.common._
+import docspell.joex.Config
+import docspell.joex.scheduler.Task
+import docspell.store.queue._
+import docspell.store.records._
+
+object HouseKeepingTask {
+  private val periodicId = Ident.unsafe("docspell-houskeeping")
+  val systemGroup: Ident = Ident.unsafe("docspell-system")
+
+  val taskName: Ident = Ident.unsafe("housekeeping")
+
+  def apply[F[_]: Sync: ContextShift](cfg: Config): Task[F, Unit, Unit] =
+    log[F](_.info(s"Running house-keeping task now"))
+      .flatMap(_ => CleanupInvitesTask(cfg))
+
+  def onCancel[F[_]: Sync: ContextShift]: Task[F, Unit, Unit] =
+    Task(_.logger.warn("Cancelling background task"))
+
+  def submit[F[_]: Sync](
+      pstore: PeriodicTaskStore[F],
+      ce: CalEvent
+  ): F[Unit] = {
+    val makeJob =
+      RPeriodicTask.createJson(
+        true,
+        taskName,
+        systemGroup,
+        (),
+        "Docspell house-keeping",
+        systemGroup,
+        Priority.Low,
+        ce
+      )
+
+    for {
+      job <- makeJob
+      _   <- pstore.insert(job.copy(id = periodicId)).attempt
+    } yield ()
+  }
+
+  private def log[F[_]](f: Logger[F] => F[Unit]): Task[F, Unit, Unit] =
+    Task(ctx => f(ctx.logger))
+}
diff --git a/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicScheduler.scala b/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicScheduler.scala
index 6789adfa..62d0c345 100644
--- a/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicScheduler.scala
+++ b/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicScheduler.scala
@@ -4,6 +4,7 @@ import fs2._
 import fs2.concurrent.SignallingRef
 import cats.effect._
 
+import docspell.joexapi.client.JoexClient
 import docspell.store.queue._
 
 /** A periodic scheduler takes care to submit periodic tasks to the
@@ -32,14 +33,16 @@ object PeriodicScheduler {
 
   def create[F[_]: ConcurrentEffect: ContextShift](
       cfg: PeriodicSchedulerConfig,
+      sch: Scheduler[F],
       queue: JobQueue[F],
       store: PeriodicTaskStore[F],
+      client: JoexClient[F],
       timer: Timer[F]
   ): Resource[F, PeriodicScheduler[F]] =
     for {
       waiter <- Resource.liftF(SignallingRef(true))
       state  <- Resource.liftF(SignallingRef(PeriodicSchedulerImpl.emptyState[F]))
-      psch = new PeriodicSchedulerImpl[F](cfg, queue, store, waiter, state, timer)
+      psch = new PeriodicSchedulerImpl[F](cfg, sch, queue, store, client, waiter, state, timer)
       _ <- Resource.liftF(psch.init)
     } yield psch
 
diff --git a/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicSchedulerImpl.scala b/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicSchedulerImpl.scala
index fe0c5c39..f8de3c8c 100644
--- a/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicSchedulerImpl.scala
+++ b/modules/joex/src/main/scala/docspell/joex/scheduler/PeriodicSchedulerImpl.scala
@@ -9,45 +9,18 @@ import com.github.eikek.fs2calev._
 
 import docspell.common._
 import docspell.common.syntax.all._
+import docspell.joexapi.client.JoexClient
 import docspell.store.queue._
 import docspell.store.records.RPeriodicTask
 
 import PeriodicSchedulerImpl.State
 
-/*
-onStartUp:
-- remove worker value from all of the current
-
-Loop:
-- get earliest pjob
-- if none: stop
-- if triggered:
-  - mark worker, restart loop on fail
-  - submit new job
-    - check for non-final jobs of that name
-    - if exist: log info
-    - if not exist: submit
-  - update next trigger (in both cases)
-  - remove worker
-  - restart loop
-- if future
-  - schedule notify
-  - stop loop
-
-
-onNotify:
-- cancel current scheduled notify
-- start Loop
-
-
-onShutdown:
-- nothing to do
- */
-
 final class PeriodicSchedulerImpl[F[_]: ConcurrentEffect: ContextShift](
     val config: PeriodicSchedulerConfig,
+    sch: Scheduler[F],
     queue: JobQueue[F],
     store: PeriodicTaskStore[F],
+    client: JoexClient[F],
     waiter: SignallingRef[F, Boolean],
     state: SignallingRef[F, State[F]],
     timer: Timer[F]
@@ -91,15 +64,18 @@ final class PeriodicSchedulerImpl[F[_]: ConcurrentEffect: ContextShift](
         _   <- logger.fdebug(s"Looking for next periodic task")
         go <- logThrow("Error getting next task")(
           store
-            .takeNext(config.name)
+            .takeNext(config.name, None)
             .use({
-              case Some(pj) =>
+              case Marked.Found(pj) =>
                 logger
                   .fdebug(s"Found periodic task '${pj.subject}/${pj.timer.asString}'") *>
                   (if (isTriggered(pj, now)) submitJob(pj)
-                   else scheduleNotify(pj)).map(_ => true)
-              case None =>
+                   else scheduleNotify(pj).map(_ => false))
+              case Marked.NotFound =>
                 logger.fdebug("No periodic task found") *> false.pure[F]
+              case Marked.NotMarkable =>
+                logger.fdebug("Periodic job cannot be marked. Trying again.") *> true
+                  .pure[F]
             })
         )
       } yield go
@@ -123,32 +99,44 @@ final class PeriodicSchedulerImpl[F[_]: ConcurrentEffect: ContextShift](
   }
 
   def isTriggered(pj: RPeriodicTask, now: Timestamp): Boolean =
-    pj.timer.contains(now.value)
+    pj.nextrun < now
 
-  def submitJob(pj: RPeriodicTask): F[Unit] =
+  def submitJob(pj: RPeriodicTask): F[Boolean] =
     store
       .findNonFinalJob(pj.id)
       .flatMap({
         case Some(job) =>
           logger.finfo[F](
             s"There is already a job with non-final state '${job.state}' in the queue"
-          )
+          ) *> scheduleNotify(pj) *> false.pure[F]
 
         case None =>
           logger.finfo[F](s"Submitting job for periodic task '${pj.task.id}'") *>
-            pj.toJob.flatMap(queue.insert)
+            pj.toJob.flatMap(queue.insert) *> notifyJoex *> true.pure[F]
       })
 
+  def notifyJoex: F[Unit] =
+    sch.notifyChange *> store.findJoexNodes.flatMap(
+      _.traverse(n => client.notifyJoexIgnoreErrors(n.url)).map(_ => ())
+    )
+
   def scheduleNotify(pj: RPeriodicTask): F[Unit] =
-    ConcurrentEffect[F]
-      .start(
-        CalevFs2
-          .sleep[F](pj.timer)
-          .evalMap(_ => notifyChange)
-          .compile
-          .drain
-      )
-      .flatMap(fb => state.modify(_.setNotify(fb)))
+    Timestamp
+      .current[F]
+      .flatMap(now =>
+        logger.fdebug(
+          s"Scheduling next notify for timer ${pj.timer.asString} -> ${pj.timer.nextElapse(now.toUtcDateTime)}"
+        )
+      ) *>
+      ConcurrentEffect[F]
+        .start(
+          CalevFs2
+            .sleep[F](pj.timer)
+            .evalMap(_ => notifyChange)
+            .compile
+            .drain
+        )
+        .flatMap(fb => state.modify(_.setNotify(fb)))
 
   def cancelNotify: F[Unit] =
     state
diff --git a/modules/joexapi/src/main/scala/docspell/joexapi/client/JoexClient.scala b/modules/joexapi/src/main/scala/docspell/joexapi/client/JoexClient.scala
index 964d4691..02a4c2cf 100644
--- a/modules/joexapi/src/main/scala/docspell/joexapi/client/JoexClient.scala
+++ b/modules/joexapi/src/main/scala/docspell/joexapi/client/JoexClient.scala
@@ -3,6 +3,7 @@ package docspell.joexapi.client
 import cats.implicits._
 import cats.effect._
 import docspell.common.{Ident, LenientUri}
+import docspell.common.syntax.all._
 import org.http4s.{Method, Request, Uri}
 import org.http4s.client.Client
 import org.http4s.client.blaze.BlazeClientBuilder
@@ -28,21 +29,24 @@ object JoexClient {
     new JoexClient[F] {
       def notifyJoex(base: LenientUri): F[Unit] = {
         val notifyUrl = base / "api" / "v1" / "notify"
-        val req = Request[F](Method.POST, uri(notifyUrl))
-        client.expect[String](req).map(_ => ())
+        val req       = Request[F](Method.POST, uri(notifyUrl))
+        logger.fdebug(s"Notify joex at ${notifyUrl.asString}") *>
+          client.expect[String](req).map(_ => ())
       }
 
       def notifyJoexIgnoreErrors(base: LenientUri): F[Unit] =
         notifyJoex(base).attempt.map {
           case Right(()) => ()
           case Left(ex) =>
-            logger.warn(s"Notifying Joex instance '${base.asString}' failed: ${ex.getMessage}")
+            logger.warn(
+              s"Notifying Joex instance '${base.asString}' failed: ${ex.getMessage}"
+            )
             ()
         }
 
       def cancelJob(base: LenientUri, job: Ident): F[Unit] = {
         val cancelUrl = base / "api" / "v1" / "job" / job.id / "cancel"
-        val req = Request[F](Method.POST, uri(cancelUrl))
+        val req       = Request[F](Method.POST, uri(cancelUrl))
         client.expect[String](req).map(_ => ())
       }
 
@@ -52,4 +56,4 @@ object JoexClient {
 
   def resource[F[_]: ConcurrentEffect](ec: ExecutionContext): Resource[F, JoexClient[F]] =
     BlazeClientBuilder[F](ec).resource.map(apply[F])
-}
\ No newline at end of file
+}
diff --git a/modules/microsite/docs/dev/adr.md b/modules/microsite/docs/dev/adr.md
index 285571da..20c149b0 100644
--- a/modules/microsite/docs/dev/adr.md
+++ b/modules/microsite/docs/dev/adr.md
@@ -16,3 +16,4 @@ title: ADRs
   - [0009 Convert Office Files](adr/0009_convert_office_docs)
   - [0010 Convert Image Files](adr/0010_convert_image_files)
   - [0011 Extract Text](adr/0011_extract_text)
+- [0012 Periodic Tasks](adr/0012_periodic_tasks)
diff --git a/modules/microsite/docs/dev/adr/0012_periodic_tasks.md b/modules/microsite/docs/dev/adr/0012_periodic_tasks.md
new file mode 100644
index 00000000..5edd559c
--- /dev/null
+++ b/modules/microsite/docs/dev/adr/0012_periodic_tasks.md
@@ -0,0 +1,102 @@
+---
+layout: docs
+title: Periodic Tasks
+---
+
+# Periodic Tasks
+
+## Context and Problem Statement
+
+Currently there is a `Scheduler` that consumes tasks off a queue in
+the database. This allows multiple job executors running in parallel
+racing for the next job to execute. This is for executing tasks
+immediately – as long as there are enough resource.
+
+What is missing, is a component that maintains periodic tasks. The
+reason for this is to have house keeping tasks that run regularily and
+clean up stale or unused data. Later, users should be able to create
+periodic tasks, for example to read e-mails from an inbox.
+
+The problem is again, that it must work with multiple job executor
+instances running at the same time. This is the same pattern as with
+the `Scheduler`: it must be ensured that only one task is used at a
+time. Multiple job exectuors must not schedule a perdiodic task more
+than once. If a periodic tasks takes longer than the time between
+runs, it must wait for the next interval.
+
+
+## Considered Options
+
+1. Adding a `timer` and `nextrun` field to the current `job` table
+2. Creating a separate table for periodic tasks
+
+## Decision Outcome
+
+The 2. option.
+
+For internal housekeeping tasks, it may suffice to reuse the existing
+`job` queue by adding more fields such that a job may be considered
+periodic. But this conflates with what the `Scheduler` is doing now
+(executing tasks as soon as possible while being bound to some
+resources) with a completely different subject.
+
+There will be a new `PeriodicScheduler` that works on a new table in
+the database that is representing periodic tasks. This table will
+share fields with the `job` table to be able to create `RJob`
+instances. This new component is only taking care of periodically
+submitting jobs to the job queue such that the `Scheduler` will
+eventually pick it up and run it.
+
+```sql
+CREATE TABLE "periodic_task" (
+  "id" varchar(254) not null primary key,
+  "enabled" boolean not null,
+  "task" varchar(254) not null,
+  "group_" varchar(254) not null,
+  "args" text not null,
+  "subject" varchar(254) not null,
+  "submitter" varchar(254) not null,
+  "priority" int not null,
+  "worker" varchar(254),
+  "marked" timestamp,
+  "timer" varchar(254) not null,
+  "nextrun" timestamp not null,
+  "created" timestamp not null
+);
+```
+
+Preparing for other features, periodic tasks will be created by users.
+It should be possible to disable/enable them. The next 6 properties
+are needed to insert jobs into the `job` table. The `worker` field
+(and `marked`) are used to mark a periodic job as "being worked on by
+a job executor".
+
+The `timer` is the schedule, which is a
+[systemd-like](https://man.cx/systemd.time#heading7) calendar event
+string. This is parsed by [this
+library](https://github.com/eikek/calev). The `nextrun` field will
+store the timestamp of the next time the task would need to be
+executed. This is needed to query this table for the newest task.
+
+The `PeriodicScheduler` works roughly like this:
+
+On startup:
+- Remove stale worker values. If the process has been killed, there
+  may be marked tasks which must be cleared now.
+
+Main-Loop:
+0. Cancel current scheduled notify (see 4. below)
+1. get next (= earliest & enabled) periodic job
+2. if none: stop
+3. if triggered (= `nextrun <= 'now'`):
+  - Mark periodic task. On fail: goto 1.
+  - Submit new job into the jobqueue:
+    - Update `nextrun` field
+    - Check for non-final jobs of that name. This is required to not
+      run the same periodic task multiple times concurrently.
+      - if exist: goto 4.
+      - if not exist: submit job
+  - Unmark periodic task
+4. if future
+  - schedule notify: notify self to run again next time the task
+    schedule triggers
diff --git a/modules/microsite/docs/dev/adr/template.md b/modules/microsite/docs/dev/adr/template.md
index 25696bbe..d531e39e 100644
--- a/modules/microsite/docs/dev/adr/template.md
+++ b/modules/microsite/docs/dev/adr/template.md
@@ -1,3 +1,8 @@
+---
+layout: docs
+title: Short Title
+---
+
 # [short title of solved problem and solution]
 
 * Status: [proposed | rejected | accepted | deprecated | … | superseded by [ADR-0005](0005-example.md)] <!-- optional -->
diff --git a/modules/store/src/main/scala/docspell/store/impl/Column.scala b/modules/store/src/main/scala/docspell/store/impl/Column.scala
index 9d697bf4..a42a09a3 100644
--- a/modules/store/src/main/scala/docspell/store/impl/Column.scala
+++ b/modules/store/src/main/scala/docspell/store/impl/Column.scala
@@ -30,6 +30,9 @@ case class Column(name: String, ns: String = "", alias: String = "") {
   def is(c: Column): Fragment =
     f ++ fr"=" ++ c.f
 
+  def isNot[A: Put](value: A): Fragment =
+    f ++ fr"<> $value"
+
   def isNull: Fragment =
     f ++ fr"is null"
 
diff --git a/modules/store/src/main/scala/docspell/store/queries/QPeriodicTask.scala b/modules/store/src/main/scala/docspell/store/queries/QPeriodicTask.scala
index 248afcfe..e52c27cc 100644
--- a/modules/store/src/main/scala/docspell/store/queries/QPeriodicTask.scala
+++ b/modules/store/src/main/scala/docspell/store/queries/QPeriodicTask.scala
@@ -1,26 +1,27 @@
 package docspell.store.queries
 
-//import cats.implicits._
 import docspell.common._
-//import docspell.common.syntax.all._
 import docspell.store.impl.Implicits._
 import docspell.store.records._
 import doobie._
 import doobie.implicits._
-//import org.log4s._
 
 object QPeriodicTask {
-//  private[this] val logger = getLogger
 
   def clearWorkers(name: Ident): ConnectionIO[Int] = {
     val worker = RPeriodicTask.Columns.worker
     updateRow(RPeriodicTask.table, worker.is(name), worker.setTo[Ident](None)).update.run
   }
 
-  def setWorker(pid: Ident, name: Ident): ConnectionIO[Int] = {
+  def setWorker(pid: Ident, name: Ident, ts: Timestamp): ConnectionIO[Int] = {
     val id     = RPeriodicTask.Columns.id
     val worker = RPeriodicTask.Columns.worker
-    updateRow(RPeriodicTask.table, and(id.is(pid), worker.isNull), worker.setTo(name)).update.run
+    val marked = RPeriodicTask.Columns.marked
+    updateRow(
+      RPeriodicTask.table,
+      and(id.is(pid), worker.isNull),
+      commas(worker.setTo(name), marked.setTo(ts))
+    ).update.run
   }
 
   def unsetWorker(
@@ -37,10 +38,17 @@ object QPeriodicTask {
     ).update.run
   }
 
-  def findNext: ConnectionIO[Option[RPeriodicTask]] = {
-    val order = orderBy(RPeriodicTask.Columns.nextrun.f) ++ fr"ASC"
+  def findNext(excl: Option[Ident]): ConnectionIO[Option[RPeriodicTask]] = {
+    val enabled = RPeriodicTask.Columns.enabled
+    val pid     = RPeriodicTask.Columns.id
+    val order   = orderBy(RPeriodicTask.Columns.nextrun.f) ++ fr"ASC"
+
+    val where = excl match {
+      case Some(id) => and(pid.isNot(id), enabled.is(true))
+      case None     => enabled.is(true)
+    }
     val sql =
-      selectSimple(RPeriodicTask.Columns.all, RPeriodicTask.table, Fragment.empty) ++ order
+      selectSimple(RPeriodicTask.Columns.all, RPeriodicTask.table, where) ++ order
     sql.query[RPeriodicTask].streamWithChunkSize(2).take(1).compile.last
   }
 
diff --git a/modules/store/src/main/scala/docspell/store/queue/JobQueue.scala b/modules/store/src/main/scala/docspell/store/queue/JobQueue.scala
index f0a9d722..1eaf2cb7 100644
--- a/modules/store/src/main/scala/docspell/store/queue/JobQueue.scala
+++ b/modules/store/src/main/scala/docspell/store/queue/JobQueue.scala
@@ -29,7 +29,7 @@ object JobQueue {
           worker: Ident,
           retryPause: Duration
       ): F[Option[RJob]] =
-        logger.fdebug("Select next job") *> QJob.takeNextJob(store)(prio, worker, retryPause)
+        logger.ftrace("Select next job") *> QJob.takeNextJob(store)(prio, worker, retryPause)
 
       def insert(job: RJob): F[Unit] =
         store
diff --git a/modules/store/src/main/scala/docspell/store/queue/Marked.scala b/modules/store/src/main/scala/docspell/store/queue/Marked.scala
new file mode 100644
index 00000000..2b634198
--- /dev/null
+++ b/modules/store/src/main/scala/docspell/store/queue/Marked.scala
@@ -0,0 +1,17 @@
+package docspell.store.queue
+
+sealed trait Marked[+A] {}
+
+object Marked {
+
+  final case class Found[A](value: A) extends Marked[A]
+
+  final case object NotFound extends Marked[Nothing]
+
+  final case object NotMarkable extends Marked[Nothing]
+
+
+  def found[A](v: A): Marked[A] = Found(v)
+  def notFound[A]: Marked[A] = NotFound
+  def notMarkable[A]: Marked[A] = NotMarkable
+}
diff --git a/modules/store/src/main/scala/docspell/store/queue/PeriodicTaskStore.scala b/modules/store/src/main/scala/docspell/store/queue/PeriodicTaskStore.scala
index 477cce03..787ec6cf 100644
--- a/modules/store/src/main/scala/docspell/store/queue/PeriodicTaskStore.scala
+++ b/modules/store/src/main/scala/docspell/store/queue/PeriodicTaskStore.scala
@@ -2,7 +2,6 @@ package docspell.store.queue
 
 import cats.effect._
 import cats.implicits._
-import fs2.Stream
 import org.log4s.getLogger
 import com.github.eikek.fs2calev._
 import docspell.common._
@@ -20,7 +19,10 @@ trait PeriodicTaskStore[F[_]] {
     * care of unmarking the task after use and updating `nextRun` with
     * the next timestamp.
     */
-  def takeNext(worker: Ident): Resource[F, Option[RPeriodicTask]]
+  def takeNext(
+      worker: Ident,
+      excludeId: Option[Ident]
+  ): Resource[F, Marked[RPeriodicTask]]
 
   def clearMarks(name: Ident): F[Unit]
 
@@ -33,6 +35,8 @@ trait PeriodicTaskStore[F[_]] {
   /** Adds the task only if it not already exists.
     */
   def add(task: RPeriodicTask): F[AddResult]
+
+  def findJoexNodes: F[Vector[RNode]]
 }
 
 object PeriodicTaskStore {
@@ -40,38 +44,37 @@ object PeriodicTaskStore {
 
   def create[F[_]: Sync](store: Store[F]): Resource[F, PeriodicTaskStore[F]] =
     Resource.pure[F, PeriodicTaskStore[F]](new PeriodicTaskStore[F] {
-      println(s"$store")
 
-      def takeNext(worker: Ident): Resource[F, Option[RPeriodicTask]] = {
-        val chooseNext: F[Either[String, Option[RPeriodicTask]]] =
-          getNext.flatMap {
+      def takeNext(
+          worker: Ident,
+          excludeId: Option[Ident]
+      ): Resource[F, Marked[RPeriodicTask]] = {
+        val chooseNext: F[Marked[RPeriodicTask]] =
+          getNext(excludeId).flatMap {
             case Some(pj) =>
               mark(pj.id, worker).map {
-                case true  => Right(Some(pj.copy(worker = worker.some)))
-                case false => Left("Cannot mark periodic task")
+                case true  => Marked.found(pj.copy(worker = worker.some))
+                case false => Marked.notMarkable
               }
             case None =>
-              val result: Either[String, Option[RPeriodicTask]] =
-                Right(None)
-              result.pure[F]
+              Marked.notFound.pure[F]
           }
-        val get =
-          Stream.eval(chooseNext).repeat.take(10).find(_.isRight).compile.lastOrError
-        val r = Resource.make(get)({
-          case Right(Some(pj)) => unmark(pj)
-          case _               => ().pure[F]
+
+        Resource.make(chooseNext)({
+          case Marked.Found(pj) => unmark(pj)
+          case _                => ().pure[F]
         })
-        r.flatMap {
-          case Right(job) => Resource.pure(job)
-          case Left(err)  => Resource.liftF(Sync[F].raiseError(new Exception(err)))
-        }
       }
 
-      def getNext: F[Option[RPeriodicTask]] =
-        store.transact(QPeriodicTask.findNext)
+      def getNext(excl: Option[Ident]): F[Option[RPeriodicTask]] =
+        store.transact(QPeriodicTask.findNext(excl))
 
       def mark(pid: Ident, name: Ident): F[Boolean] =
-        store.transact(QPeriodicTask.setWorker(pid, name)).map(_ > 0)
+        Timestamp
+          .current[F]
+          .flatMap(now =>
+            store.transact(QPeriodicTask.setWorker(pid, name, now)).map(_ > 0)
+          )
 
       def unmark(job: RPeriodicTask): F[Unit] =
         for {
@@ -98,16 +101,15 @@ object PeriodicTaskStore {
 
       def insert(task: RPeriodicTask): F[Unit] = {
         val update = store.transact(RPeriodicTask.update(task))
-        val insertAttempt = store.transact(RPeriodicTask.insert(task))
-          .attempt.map {
-            case Right(n) => n > 0
-            case Left(_) => false
-          }
+        val insertAttempt = store.transact(RPeriodicTask.insert(task)).attempt.map {
+          case Right(n) => n > 0
+          case Left(_)  => false
+        }
 
         for {
-          n1 <- update
+          n1  <- update
           ins <- if (n1 == 0) insertAttempt else true.pure[F]
-          _ <- if (ins) 1.pure[F] else update
+          _   <- if (ins) 1.pure[F] else update
         } yield ()
       }
 
@@ -116,5 +118,9 @@ object PeriodicTaskStore {
         val exists = RPeriodicTask.exists(task.id)
         store.add(insert, exists)
       }
+
+      def findJoexNodes: F[Vector[RNode]] =
+        store.transact(RNode.findAll(NodeType.Joex))
+
     })
 }
diff --git a/modules/store/src/main/scala/docspell/store/records/RInvitation.scala b/modules/store/src/main/scala/docspell/store/records/RInvitation.scala
index 98d48a51..37764d0c 100644
--- a/modules/store/src/main/scala/docspell/store/records/RInvitation.scala
+++ b/modules/store/src/main/scala/docspell/store/records/RInvitation.scala
@@ -46,4 +46,7 @@ object RInvitation {
       _   <- delete(invite)
     } yield inv > 0
   }
+
+  def deleteOlderThan(ts: Timestamp): ConnectionIO[Int] =
+    deleteFrom(table, created.isLt(ts)).update.run
 }
diff --git a/modules/store/src/main/scala/docspell/store/records/RPeriodicTask.scala b/modules/store/src/main/scala/docspell/store/records/RPeriodicTask.scala
index 57d37e20..a510904b 100644
--- a/modules/store/src/main/scala/docspell/store/records/RPeriodicTask.scala
+++ b/modules/store/src/main/scala/docspell/store/records/RPeriodicTask.scala
@@ -8,6 +8,7 @@ import com.github.eikek.calev.CalEvent
 import docspell.common._
 import docspell.store.impl.Column
 import docspell.store.impl.Implicits._
+import io.circe.Encoder
 
 /** A periodic task is a special job description, that shares a few
   * properties of a `RJob`. It must provide all information to create
@@ -62,8 +63,6 @@ object RPeriodicTask {
       subject: String,
       submitter: Ident,
       priority: Priority,
-      worker: Option[Ident],
-      marked: Option[Timestamp],
       timer: CalEvent
   ): F[RPeriodicTask] =
     Ident
@@ -81,8 +80,8 @@ object RPeriodicTask {
               subject,
               submitter,
               priority,
-              worker,
-              marked,
+              None,
+              None,
               timer,
               timer
                 .nextElapse(now.atZone(Timestamp.UTC))
@@ -94,6 +93,18 @@ object RPeriodicTask {
           }
       )
 
+  def createJson[F[_]: Sync, A](
+      enabled: Boolean,
+      task: Ident,
+      group: Ident,
+      args: A,
+      subject: String,
+      submitter: Ident,
+      priority: Priority,
+      timer: CalEvent
+  )(implicit E: Encoder[A]): F[RPeriodicTask] =
+    create[F](enabled, task, group, E(args).noSpaces, subject, submitter, priority, timer)
+
   val table = fr"periodic_task"
 
   object Columns {
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index dea1cff3..7d221bd2 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -38,10 +38,13 @@ object Dependencies {
   val ViewerJSVersion = "0.5.8"
 
 
-  val calev = Seq(
+  val calevCore = Seq(
     "com.github.eikek" %% "calev-core" % CalevVersion,
+  )
+  val calevFs2 = Seq(
     "com.github.eikek" %% "calev-fs2" % CalevVersion
   )
+  val calev = calevFs2 ++ calevCore
 
   val jclOverSlf4j = Seq(
     "org.slf4j" % "jcl-over-slf4j" % Slf4jVersion