diff --git a/app/controllers/RelayRound.scala b/app/controllers/RelayRound.scala
index 45a72efe4251..051783c452cf 100644
--- a/app/controllers/RelayRound.scala
+++ b/app/controllers/RelayRound.scala
@@ -227,11 +227,7 @@ final class RelayRound(
       }(Unauthorized, Forbidden)
 
   def stats(id: RelayRoundId) = Open:
-    env.relay.stats
-      .get(id)
-      .map: stats =>
-        import lila.relay.JsonView.given
-        JsonOk(stats)
+    env.relay.statsJson(id).map(JsonOk)
 
   private def WithRoundAndTour(
       @nowarn ts: String,
@@ -274,7 +270,7 @@ final class RelayRound(
           case VideoEmbed.Auto =>
             fuccess:
               rt.tour.pinnedStream
-                .ifFalse(rt.round.finished)
+                .ifFalse(rt.round.isFinished)
                 .flatMap(_.upstream)
                 .map(_.urls(netDomain).toPair)
           case VideoEmbed.No => fuccess(none)
diff --git a/bin/mongodb/relay-round-finishedAt.js b/bin/mongodb/relay-round-finishedAt.js
new file mode 100644
index 000000000000..064580b66663
--- /dev/null
+++ b/bin/mongodb/relay-round-finishedAt.js
@@ -0,0 +1,6 @@
+db.relay.find({ finished: true, finishedAt: { $exists: false } }).forEach(function(relay) {
+  const startAt = relay.startedAt || relay.startsAt || relay.createdAt;
+  const duration = 1000 * 60 * 60 * 3; // 3 hours
+  const finishAt = new Date(startAt.getTime() + duration);
+  db.relay.updateOne({ _id: relay._id }, { $set: { finishedAt: finishAt } });
+});
diff --git a/modules/common/src/main/mon.scala b/modules/common/src/main/mon.scala
index 91f2b7585d96..c0826581fa73 100644
--- a/modules/common/src/main/mon.scala
+++ b/modules/common/src/main/mon.scala
@@ -283,6 +283,7 @@ object mon:
     private def relay(official: Boolean, id: RelayTourId, slug: String) =
       tags("by" -> by(official), "slug" -> s"$slug/$id")
     def ongoing(official: Boolean) = gauge("relay.ongoing").withTag("by", by(official))
+    val crowdMonitor               = gauge("relay.crowdMonitor").withoutTags()
     def games(official: Boolean, id: RelayTourId, slug: String) =
       gauge("relay.games").withTags(relay(official, id, slug))
     def moves(official: Boolean, id: RelayTourId, slug: String) =
diff --git a/modules/db/src/main/dsl.scala b/modules/db/src/main/dsl.scala
index 96f0b71c5ecc..01cb17b18c02 100644
--- a/modules/db/src/main/dsl.scala
+++ b/modules/db/src/main/dsl.scala
@@ -105,6 +105,12 @@ trait dsl:
     "$unset" -> fields.nonEmpty.so($doc(fields.map(k => (k, BSONString("")))))
   def $unset(field: String, fields: String*): Bdoc = $doc:
     "$unset" -> $doc((Seq(field) ++ fields).map(k => (k, BSONString(""))))
+
+  def $unsetCompute[A](prev: A, next: A, fields: (String, A => Option[?])*): Bdoc =
+    $unset:
+      fields.flatMap: (key, accessor) =>
+        (accessor(prev).isDefined && accessor(next).isEmpty).option(key)
+
   def $setBoolOrUnset(field: String, value: Boolean): Bdoc =
     if value then $set(field -> true) else $unset(field)
   def $setsAndUnsets(items: (String, Option[BSONValue])*): Bdoc =
diff --git a/modules/relay/src/main/Env.scala b/modules/relay/src/main/Env.scala
index ab2ab24bc00e..eb5370eca845 100644
--- a/modules/relay/src/main/Env.scala
+++ b/modules/relay/src/main/Env.scala
@@ -65,8 +65,6 @@ final class Env(
 
   lazy val listing: RelayListing = wire[RelayListing]
 
-  lazy val stats = wire[RelayStatsApi]
-
   lazy val api: RelayApi = wire[RelayApi]
 
   lazy val tourStream: RelayTourStream = wire[RelayTourStream]
@@ -101,6 +99,10 @@ final class Env(
 
   private lazy val delay = wire[RelayDelay]
 
+  // eager init to start the scheduler
+  private val stats = wire[RelayStatsApi]
+  export stats.{ getJson as statsJson }
+
   import SettingStore.CredentialsOption.given
   val proxyCredentials = settingStore[Option[Credentials]](
     "relayProxyCredentials",
diff --git a/modules/relay/src/main/JsonView.scala b/modules/relay/src/main/JsonView.scala
index 42c97b8a96cb..d10e63382bb2 100644
--- a/modules/relay/src/main/JsonView.scala
+++ b/modules/relay/src/main/JsonView.scala
@@ -166,14 +166,15 @@ object JsonView:
         "slug"      -> r.slug,
         "createdAt" -> r.createdAt
       )
-      .add("finished" -> r.finished)
-      .add("ongoing" -> (r.hasStarted && !r.finished))
+      .add("finishedAt" -> r.finishedAt)
+      .add("finished" -> r.isFinished) // BC
+      .add("ongoing" -> (r.hasStarted && !r.isFinished))
       .add("startsAt" -> r.startsAtTime.orElse(r.startedAt))
       .add("startsAfterPrevious" -> r.startsAfterPrevious)
 
-  given OWrites[RelayStats.RoundStats] = OWrites: r =>
+  def statsJson(stats: RelayStats.RoundStats) =
     Json.obj(
-      "viewers" -> r.viewers.map: (minute, crowd) =>
+      "viewers" -> stats.viewers.map: (minute, crowd) =>
         Json.arr(minute * 60, crowd)
     )
 
diff --git a/modules/relay/src/main/RelayApi.scala b/modules/relay/src/main/RelayApi.scala
index 8da8983051cf..2a12f42e3dd4 100644
--- a/modules/relay/src/main/RelayApi.scala
+++ b/modules/relay/src/main/RelayApi.scala
@@ -316,12 +316,12 @@ final class RelayApi(
         round   <- copyRoundSourceSettings(updated)
         _       <- (from.name != round.name).so(studyApi.rename(round.studyId, round.name.into(StudyName)))
         setters <- tryBdoc(round).toEither.toFuture
-        unsetters = (from.caption.isDefined && updated.caption.isEmpty).option("caption").toList
-        _ <- roundRepo.coll.update.one($id(round.id), $set(setters) ++ $unset(unsetters)).void
+        unsets = $unsetCompute(from, updated, ("caption", _.caption), ("finishedAt", _.finishedAt))
+        _ <- roundRepo.coll.update.one($id(round.id), $set(setters) ++ unsets).void
         _ <- (round.sync.playing != from.sync.playing)
           .so(sendToContributors(round.id, "relaySync", jsonView.sync(round)))
         _                <- denormalizeTour(round.tourId)
-        nextRoundToStart <- round.finished.so(nextRoundThatStartsAfterThisOneCompletes(round))
+        nextRoundToStart <- round.isFinished.so(nextRoundThatStartsAfterThisOneCompletes(round))
         _                <- nextRoundToStart.so(next => requestPlay(next.id, v = true))
       yield
         round.sync.log.events.lastOption
diff --git a/modules/relay/src/main/RelayFetch.scala b/modules/relay/src/main/RelayFetch.scala
index be54491fe0c0..c3be1a1c90a7 100644
--- a/modules/relay/src/main/RelayFetch.scala
+++ b/modules/relay/src/main/RelayFetch.scala
@@ -109,9 +109,9 @@ final private class RelayFetch(
           nbGamesFinished > nbGamesUnstarted
         noMoreGamesSelected = games.isEmpty && allGamesInSource.nonEmpty
         autoFinishNow       = rt.round.hasStarted && (allGamesFinishedOrUnstarted || noMoreGamesSelected)
-        roundUpdate = updating:
-          _.withSync(_.addLog(SyncLog.event(res.nbMoves, none)))
-            .copy(finished = autoFinishNow)
+        roundUpdate = updating: r =>
+          r.withSync(_.addLog(SyncLog.event(res.nbMoves, none)))
+            .copy(finishedAt = r.finishedAt.orElse(autoFinishNow.option(nowInstant)))
       yield res -> roundUpdate
       syncFu
         .recover:
diff --git a/modules/relay/src/main/RelayListing.scala b/modules/relay/src/main/RelayListing.scala
index cb3b1a34dd1c..0fd6f41545b4 100644
--- a/modules/relay/src/main/RelayListing.scala
+++ b/modules/relay/src/main/RelayListing.scala
@@ -147,7 +147,7 @@ final class RelayListing(
       yield
         spotlightCache = active
           .filter(_.tour.spotlight.exists(_.enabled))
-          .filterNot(_.display.finished)
+          .filterNot(_.display.isFinished)
           .filter: tr =>
             tr.display.hasStarted || tr.display.startsAtTime.exists(_.isBefore(nowInstant.plusMinutes(30)))
         active
@@ -256,7 +256,7 @@ private object RelayListing:
         .match
           case None => trs.rounds.headOption
           case Some(last) =>
-            trs.rounds.find(!_.finished) match
+            trs.rounds.find(!_.isFinished) match
               case None => last.some
               case Some(next) =>
                 if next.startsAtTime.exists(_.isBefore(nowInstant.plusHours(1)))
diff --git a/modules/relay/src/main/RelayPush.scala b/modules/relay/src/main/RelayPush.scala
index abfb750329e8..4cd479727f3c 100644
--- a/modules/relay/src/main/RelayPush.scala
+++ b/modules/relay/src/main/RelayPush.scala
@@ -13,7 +13,6 @@ import lila.study.{ ChapterPreviewApi, MultiPgn, StudyPgnImport }
 final class RelayPush(
     sync: RelaySync,
     api: RelayApi,
-    stats: RelayStatsApi,
     chapterPreview: ChapterPreviewApi,
     fidePlayers: RelayFidePlayerApi,
     playerEnrich: RelayPlayerEnrich,
@@ -61,13 +60,13 @@ final class RelayPush(
             case e: Exception => SyncLog.event(0, e.some)
         _ = if !rt.round.hasStarted && !rt.tour.official && event.hasMoves then
           irc.broadcastStart(rt.round.id, rt.fullName)
-        _ = stats.setActive(rt.round.id)
         allGamesFinished <- (games.nonEmpty && games.forall(_.points.isDefined)).so:
           chapterPreview.dataList(rt.round.studyId).map(_.forall(_.finished))
         round <- api.update(rt.round): r1 =>
-          val r2 = r1.withSync(_.addLog(event))
-          val r3 = if event.hasMoves then r2.ensureStarted.resume(rt.tour.official) else r2
-          r3.copy(finished = allGamesFinished)
+          val r2         = r1.withSync(_.addLog(event))
+          val r3         = if event.hasMoves then r2.ensureStarted.resume(rt.tour.official) else r2
+          val finishedAt = allGamesFinished.option(r3.finishedAt.|(nowInstant))
+          r3.copy(finishedAt = finishedAt)
         _ <- andSyncTargets.so(api.syncTargetsOfSource(round))
       yield ()
 
diff --git a/modules/relay/src/main/RelayRound.scala b/modules/relay/src/main/RelayRound.scala
index fe258ba5a7b0..c5c4b6b63866 100644
--- a/modules/relay/src/main/RelayRound.scala
+++ b/modules/relay/src/main/RelayRound.scala
@@ -20,9 +20,10 @@ case class RelayRound(
     startedAt: Option[Instant],
     /* at least it *looks* finished... but maybe it's not
      * sync.nextAt is used for actually synchronising */
-    finished: Boolean,
+    finishedAt: Option[Instant],
     createdAt: Instant,
     crowd: Option[Int]
+    // crowdAt: Option[Instant], // in DB but not used by RelayRound
 ):
   inline def studyId = id.into(StudyId)
 
@@ -30,6 +31,8 @@ case class RelayRound(
     val s = scalalib.StringOps.slug(name.value)
     if s.isEmpty then "-" else s
 
+  def isFinished = finishedAt.isDefined
+
   def startsAtTime = startsAt.flatMap:
     case RelayRound.Starts.At(at) => at.some
     case _                        => none
@@ -37,13 +40,13 @@ case class RelayRound(
 
   def finish =
     copy(
-      finished = true,
+      finishedAt = finishedAt.orElse(nowInstant.some),
       sync = sync.pause
     )
 
   def resume(official: Boolean) =
     copy(
-      finished = false,
+      finishedAt = none,
       sync = sync.play(official)
     )
 
diff --git a/modules/relay/src/main/RelayRoundForm.scala b/modules/relay/src/main/RelayRoundForm.scala
index 65c06a5b7ac6..0725fb0ae81b 100644
--- a/modules/relay/src/main/RelayRoundForm.scala
+++ b/modules/relay/src/main/RelayRoundForm.scala
@@ -217,7 +217,7 @@ object RelayRoundForm:
         caption = if Granter(_.StudyAdmin) then caption else relay.caption,
         sync = if relay.sync.playing then sync.play(official) else sync,
         startsAt = relayStartsAt,
-        finished = ~finished
+        finishedAt = finished.orZero.option(relay.finishedAt.|(nowInstant))
       )
 
     private def makeSync(prev: Option[RelayRound.Sync])(using Me): Sync =
@@ -241,7 +241,7 @@ object RelayRoundForm:
         sync = makeSync(none),
         createdAt = nowInstant,
         crowd = none,
-        finished = ~finished,
+        finishedAt = (~finished).option(nowInstant),
         startsAt = relayStartsAt,
         startedAt = none
       )
@@ -267,7 +267,7 @@ object RelayRoundForm:
           case ids: Upstream.Ids => ids,
         startsAt = relay.startsAtTime,
         startsAfterPrevious = relay.startsAfterPrevious.option(true),
-        finished = relay.finished.option(true),
+        finished = relay.isFinished.option(true),
         period = relay.sync.period,
         onlyRound = relay.sync.onlyRound,
         slices = relay.sync.slices,
diff --git a/modules/relay/src/main/RelayStatsApi.scala b/modules/relay/src/main/RelayStatsApi.scala
index 989eef7f9ce7..b484e4439eed 100644
--- a/modules/relay/src/main/RelayStatsApi.scala
+++ b/modules/relay/src/main/RelayStatsApi.scala
@@ -4,13 +4,13 @@ import scalalib.cache.ExpireSetMemo
 
 import lila.db.dsl.{ *, given }
 
-object RelayStats:
+private object RelayStats:
   type Minute = Int
   type Crowd  = Int
   type Graph  = List[(Minute, Crowd)]
   case class RoundStats(viewers: Graph)
 
-final class RelayStatsApi(colls: RelayColls)(using scheduler: Scheduler)(using
+private final class RelayStatsApi(colls: RelayColls)(using scheduler: Scheduler)(using
     Executor
 ):
   import RelayStats.*
@@ -28,10 +28,7 @@ final class RelayStatsApi(colls: RelayColls)(using scheduler: Scheduler)(using
           .toList
       .map(RoundStats.apply)
 
-  def setActive(id: RelayRoundId) = activeRounds.put(id)
-
-  // keep monitoring rounds for some time after they stopped syncing
-  private val activeRounds = ExpireSetMemo[RelayRoundId](2 hours)
+  def getJson(id: RelayRoundId) = get(id).map(JsonView.statsJson)
 
   private def record(): Funit = for
     crowds <- fetchRoundCrowds
@@ -63,26 +60,20 @@ final class RelayStatsApi(colls: RelayColls)(using scheduler: Scheduler)(using
   yield ()
 
   private def fetchRoundCrowds: Fu[List[(RelayRoundId, Crowd)]] =
-    val max = 500
+    val max = 200
     colls.round
       .aggregateList(maxDocs = max, _.sec): framework =>
         import framework.*
-        Match(
-          $doc(
-            $or(
-              $doc("sync.until" -> $exists(true)),
-              $inIds(activeRounds.keys)
-            ),
-            "crowd".$gt(0)
-          )
-        ) ->
-          List(Project($doc("_id" -> 1, "crowd" -> 1, "syncing" -> "$sync.until")))
+        // lila-ws sets crowdAt along with crowd
+        // so we can use crowdAt to know which rounds are being monitored
+        Match($doc("crowdAt".$gt(nowInstant.minusMinutes(1)))) ->
+          List(Project($doc("_id" -> 1, "crowd" -> 1)))
       .map: docs =>
+        lila.mon.relay.crowdMonitor.update(docs.size)
         if docs.size == max
         then logger.warn(s"RelayStats.fetchRoundCrowds: $max docs fetched")
         for
           doc   <- docs
           id    <- doc.getAsOpt[RelayRoundId]("_id")
           crowd <- doc.getAsOpt[Crowd]("crowd")
-          _ = if doc.contains("syncing") then activeRounds.put(id)
         yield (id, crowd)
diff --git a/modules/relay/src/main/ui/RelayFormUi.scala b/modules/relay/src/main/ui/RelayFormUi.scala
index b9a9b5b3d42b..e3d58d352a7f 100644
--- a/modules/relay/src/main/ui/RelayFormUi.scala
+++ b/modules/relay/src/main/ui/RelayFormUi.scala
@@ -46,7 +46,7 @@ final class RelayFormUi(helpers: Helpers, ui: RelayUi, tourUi: RelayTourUi):
             href := routes.RelayRound.edit(r.id),
             cls  := List("subnav__subitem text" -> true, "active" -> nav.roundId.has(r.id)),
             dataIcon := (
-              if r.finished then Icon.Checkmark
+              if r.isFinished then Icon.Checkmark
               else if r.hasStarted then Icon.DiscBig
               else Icon.DiscOutline
             )
diff --git a/modules/tournament/src/main/TournamentStats.scala b/modules/tournament/src/main/TournamentStats.scala
index 5332e9d8b1d2..cba23468e52f 100644
--- a/modules/tournament/src/main/TournamentStats.scala
+++ b/modules/tournament/src/main/TournamentStats.scala
@@ -15,12 +15,10 @@ final class TournamentStatsApi(
 
   private given BSONDocumentHandler[TournamentStats] = Macros.handler
 
-  private val cache = mongoCache[TourId, TournamentStats](64, "tournament:stats", 60 days, _.value) {
-    loader =>
-      _.expireAfterAccess(10 minutes)
-        .maximumSize(256)
-        .buildAsyncFuture(loader(fetch))
-  }
+  private val cache = mongoCache[TourId, TournamentStats](64, "tournament:stats", 60 days, _.value): loader =>
+    _.expireAfterAccess(10 minutes)
+      .maximumSize(256)
+      .buildAsyncFuture(loader(fetch))
 
   private def fetch(tournamentId: TourId): Fu[TournamentStats] =
     for