diff --git a/src/dstack/_internal/server/background/scheduled_tasks/compute_groups.py b/src/dstack/_internal/server/background/scheduled_tasks/compute_groups.py
index 58d6b2c8b..66e31a169 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/compute_groups.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/compute_groups.py
@@ -49,6 +49,7 @@ async def _process_next_compute_group():
             res = await session.execute(
                 select(ComputeGroupModel)
                 .where(
+                    ComputeGroupModel.lock_expires_at.is_(None),
                     ComputeGroupModel.deleted == False,
                     ComputeGroupModel.id.not_in(lockset),
                     ComputeGroupModel.last_processed_at
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/fleets.py b/src/dstack/_internal/server/background/scheduled_tasks/fleets.py
index 6b1ba7667..a1cd696b6 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/fleets.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/fleets.py
@@ -55,6 +55,7 @@ async def process_fleets():
             res = await session.execute(
                 select(FleetModel)
                 .where(
+                    FleetModel.lock_expires_at.is_(None),
                     FleetModel.deleted == False,
                     FleetModel.id.not_in(fleet_lockset),
                     FleetModel.last_processed_at
@@ -75,6 +76,7 @@ async def process_fleets():
             res = await session.execute(
                 select(InstanceModel)
                 .where(
+                    InstanceModel.lock_expires_at.is_(None),
                     InstanceModel.id.not_in(instance_lockset),
                     InstanceModel.fleet_id.in_(fleet_ids),
                     InstanceModel.deleted == False,
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/gateways.py b/src/dstack/_internal/server/background/scheduled_tasks/gateways.py
index 262f45a18..3c88d21c7 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/gateways.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/gateways.py
@@ -45,6 +45,7 @@ async def process_gateways():
             res = await session.execute(
                 select(GatewayModel)
                 .where(
+                    GatewayModel.lock_expires_at.is_(None),
                     GatewayModel.status.in_([GatewayStatus.SUBMITTED, GatewayStatus.PROVISIONING]),
                     GatewayModel.id.not_in(lockset),
                 )
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/instances.py b/src/dstack/_internal/server/background/scheduled_tasks/instances.py
index e60f81190..5c041dc2b 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/instances.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/instances.py
@@ -176,6 +176,7 @@ async def _process_next_instance():
                             InstanceModel.compute_group_id.is_not(None),
                         )
                     ),
+                    InstanceModel.lock_expires_at.is_(None),
                     InstanceModel.id.not_in(lockset),
                     InstanceModel.last_processed_at
                     < get_current_datetime() - MIN_PROCESSING_INTERVAL,
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/placement_groups.py b/src/dstack/_internal/server/background/scheduled_tasks/placement_groups.py
index 1106ce491..eafd21820 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/placement_groups.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/placement_groups.py
@@ -31,6 +31,7 @@ async def process_placement_groups():
             res = await session.execute(
                 select(PlacementGroupModel)
                 .where(
+                    PlacementGroupModel.lock_expires_at.is_(None),
                     PlacementGroupModel.fleet_deleted == True,
                     PlacementGroupModel.deleted == False,
                     PlacementGroupModel.id.not_in(lockset),
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/running_jobs.py b/src/dstack/_internal/server/background/scheduled_tasks/running_jobs.py
index 7adcabdf7..72d60b581 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/running_jobs.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/running_jobs.py
@@ -121,6 +121,7 @@ async def _process_next_running_job():
                 select(JobModel)
                 .join(JobModel.run)
                 .where(
+                    JobModel.lock_expires_at.is_(None),
                     JobModel.status.in_(
                         [JobStatus.PROVISIONING, JobStatus.PULLING, JobStatus.RUNNING]
                     ),
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/runs.py b/src/dstack/_internal/server/background/scheduled_tasks/runs.py
index 1b3313725..715c47c61 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/runs.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/runs.py
@@ -73,6 +73,8 @@
 ROLLING_DEPLOYMENT_MAX_SURGE = 1  # at most one extra replica during rolling deployment
 
 
+# NOTE: This scheduled task is going to be deprecated in favor of `RunPipeline`.
+# If this logic changes before removal, keep `pipeline_tasks/runs/__init__.py` in sync.
 async def process_runs(batch_size: int = 1):
     tasks = []
     for _ in range(batch_size):
@@ -90,6 +92,7 @@ async def _process_next_run():
             res = await session.execute(
                 select(RunModel)
                 .where(
+                    RunModel.lock_expires_at.is_(None),
                     RunModel.id.not_in(run_lockset),
                     RunModel.last_processed_at < now - MIN_PROCESSING_INTERVAL,
                     # Filter out runs that don't need to be processed.
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/submitted_jobs.py b/src/dstack/_internal/server/background/scheduled_tasks/submitted_jobs.py
index eaa452380..4f6207112 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/submitted_jobs.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/submitted_jobs.py
@@ -151,6 +151,8 @@
 last_processed_at: Optional[datetime] = None
 
 
+# NOTE: This scheduled task is going to be deprecated in favor of `JobSubmittedPipeline`.
+# If this logic changes before removal, keep `pipeline_tasks/jobs_submitted.py` in sync.
 async def process_submitted_jobs(batch_size: int = 1):
     tasks = []
     effective_batch_size = _get_effective_batch_size(batch_size)
@@ -177,6 +179,7 @@ async def _process_next_submitted_job():
                 select(JobModel)
                 .join(JobModel.run)
                 .where(
+                    JobModel.lock_expires_at.is_(None),
                     JobModel.status == JobStatus.SUBMITTED,
                     JobModel.waiting_master_job.is_not(True),
                     JobModel.id.not_in(lockset),
@@ -634,6 +637,14 @@ async def _process_new_capacity_provisioning_path(
         job=context.job,
     )
 
+    if context.fleet_model is not None and fleet_model is None:
+        await _defer_submitted_job(
+            session=session,
+            job_model=context.job_model,
+            log_message="cluster fleet is locked",
+        )
+        return None
+
     # master_job_provisioning_data is present if there is a master job.
     # master_instance_provisioning_data is present if there is a master instance (non empty cluster fleet).
     master_provisioning_data = master_job_provisioning_data or master_instance_provisioning_data
@@ -1018,6 +1029,8 @@ async def _lock_fleet_and_get_master_provisioning_data(
     )
     await sqlite_commit(session)
     fleet_model = await _refetch_cluster_master_fleet(session=session, fleet_model=fleet_model)
+    if fleet_model is None:
+        return None, None
     master_instance_provisioning_data = get_fleet_master_instance_provisioning_data(
         fleet_model=fleet_model,
         fleet_spec=fleet_spec,
@@ -1034,7 +1047,7 @@ def _get_cluster_fleet_spec(fleet_model: FleetModel) -> Optional[FleetSpec]:
 
 async def _refetch_cluster_master_fleet(
     session: AsyncSession, fleet_model: FleetModel
-) -> FleetModel:
+) -> Optional[FleetModel]:
     res = await session.execute(
         select(FleetModel)
         .where(
@@ -1050,6 +1063,9 @@ async def _refetch_cluster_master_fleet(
     )
     empty_fleet_model = res.unique().scalar()
     if empty_fleet_model is not None:
+        if empty_fleet_model.lock_expires_at is not None:
+            # Defer while a pipeline owns the empty cluster fleet.
+            return None
         return empty_fleet_model
 
     res = await session.execute(
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/terminating_jobs.py b/src/dstack/_internal/server/background/scheduled_tasks/terminating_jobs.py
index ab25c2c7d..fefadcf44 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/terminating_jobs.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/terminating_jobs.py
@@ -81,6 +81,7 @@ async def _process_next_terminating_job():
             res = await session.execute(
                 select(JobModel)
                 .where(
+                    JobModel.lock_expires_at.is_(None),
                     JobModel.id.not_in(job_lockset),
                     JobModel.status == JobStatus.TERMINATING,
                     or_(
diff --git a/src/dstack/_internal/server/background/scheduled_tasks/volumes.py b/src/dstack/_internal/server/background/scheduled_tasks/volumes.py
index 11e6f3c59..2fb35ff7b 100644
--- a/src/dstack/_internal/server/background/scheduled_tasks/volumes.py
+++ b/src/dstack/_internal/server/background/scheduled_tasks/volumes.py
@@ -34,6 +34,7 @@ async def process_submitted_volumes():
             res = await session.execute(
                 select(VolumeModel)
                 .where(
+                    VolumeModel.lock_expires_at.is_(None),
                     VolumeModel.status == VolumeStatus.SUBMITTED,
                     VolumeModel.deleted == False,
                     VolumeModel.id.not_in(lockset),