diff --git a/Makefile b/Makefile
index 6e8c538..c351c7e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 TARGET = ./cc-metric-store
 VAR = ./var/checkpoints/
-VERSION = 1.5.0
+VERSION = 1.5.3
 GIT_HASH := $(shell git rev-parse --short HEAD || echo 'development')
 CURRENT_TIME = $(shell date +"%Y-%m-%d:T%H:%M:%S")
 LD_FLAGS = '-s -X main.date=${CURRENT_TIME} -X main.version=${VERSION} -X main.commit=${GIT_HASH}'
diff --git a/ReleaseNotes.md b/ReleaseNotes.md
index acb2144..1a8822a 100644
--- a/ReleaseNotes.md
+++ b/ReleaseNotes.md
@@ -1,11 +1,49 @@
-# `cc-metric-store` version 1.5.0
+# `cc-metric-store` version 1.5.3
 
-This is a major release of `cc-metric-store`, the metric timeseries cache
+This is a bugfix release of `cc-metric-store`, the metric timeseries cache
 implementation of ClusterCockpit. Since the storage engine is now part of
 `cc-backend` we will follow the version number of `cc-backend`.
 For release specific notes visit the [ClusterCockpit Documentation](https://clusterockpit.org/docs/release/).
 
-## Breaking changes
+## Notable changes
+
+- **`-cleanup-checkpoints` CLI flag**: New flag triggers checkpoint cleanup
+  (delete or archive to Parquet) based on the configured retention and cleanup
+  settings, then exits. Useful for one-off maintenance without starting the full
+  server.
+- **GC initialised before checkpoint load**: `GOGC=15` is now set before
+  `metricstore.Init` so the garbage-collector baseline is established prior to
+  the largest allocation event (loading checkpoints from disk), reducing
+  unnecessary heap growth at startup.
+- **Dependency upgrades**: `cc-backend` updated from v1.5.0 to v1.5.3;
+  `cc-lib` updated from v2.8.0 to v2.11.0; `nats.go` bumped from v1.49.0 to
+  v1.50.0; `parquet-go` bumped from v0.28.0 to v0.29.0; various other module
+  upgrades.
+
+## Metricstore package fixes (cc-backend v1.5.0 → v1.5.3)
+
+The following fixes landed in the upstream `cc-backend/pkg/metricstore` package
+and are included via the dependency upgrade:
+
+- **WAL correctness**: Fixed WAL rotation being skipped for all nodes due to a
+  non-blocking send on a too-small channel; fixed unbound growth of WAL files
+  when a checkpointing error occurs; fixed bugs in the WAL journal pipeline.
+- **WAL throughput**: Sharded the WAL consumer for higher write throughput; added
+  buffered I/O to WAL writes.
+- **Checkpoint stability**: Paused WAL writes during binary checkpoint creation
+  to prevent message drops; restructured cleanup archiving to stay within the
+  32 k row limit of `parquet-go`.
+- **Memory**: Fixed a memory explosion caused by broken emergency-free and batch
+  aborts; reduced memory usage in the Parquet checkpoint archiver; fixed
+  preventing memory spikes in the Parquet writer during the move/archive policy.
+- **NATS**: Fixed blocking `ReceiveNats` call; fixed NATS contention under load.
+- **Shutdown**: Increased shutdown timeouts; added WAL flush interval tuning;
+  added shutdown timing logs.
+- **Observability**: Added verbose logs for `DataDoesNotAlign` errors; reduced
+  noise by demoting a missing-metric warning to debug level.
+- **Configuration**: Restored `checkpointInterval` as an optional config key.
+
+## Breaking changes (from v1.4.x)
 
 - The internal `memorystore`, `avro`, `resampler`, and `util` packages have been
   removed. The storage engine is now provided by the
@@ -14,22 +52,3 @@ For release specific notes visit the [ClusterCockpit Documentation](https://clus
   only.
 - The configuration schema has changed. Refer to `configs/config.json` for the
   updated structure.
-
-## Notable changes
-
-- **Storage engine extracted to `cc-backend` library**: The entire in-memory
-  time-series storage engine was moved to `cc-backend/pkg/metricstore`. This
-  reduces duplication in the ClusterCockpit suite and enables shared maintenance
-  of the storage layer.
-- **HealthCheck API endpoint**: New `GET /api/healthcheck/` endpoint reports the
-  health status of cluster nodes.
-- **Dynamic memory management**: Memory limits can now be adjusted at runtime via
-  a callback from the `cc-backend` library.
-- **Configuration schema validation**: The config and metric config JSON schemas
-  have been updated and are now validated against the structs they describe.
-- **Startup refactored**: Application startup has been split into `cli.go` and
-  `server.go` for clearer separation of concerns.
-- **`go fix` applied**: Codebase updated to current Go idioms.
-- **Dependency upgrades**: `nats.go` bumped from 1.36.0 to 1.47.0;
-  `cc-lib` updated to v2.8.0; `cc-backend` updated to v1.5.0; various other
-  module upgrades.