TierCache 2.1.0

Changed

• Reduced shared-monitor contention for read-only L1 freshness checks, atomic access-expiry refresh and CLOSED circuit-breaker admission while preserving entry identity, retention floors and breaker epoch accounting.
• Async singleflight followers no longer occupy API workers while waiting for the leader. Cancellation, completion and shutdown release follower registrations.
• Pub/Sub invalidations now use bounded, ordered per-cache queues over a shared worker pool. Message, encoded-byte and recovery attachment budgets prevent unbounded retention; overflow triggers explicit gap recovery. Spring and Micronaut expose the dispatch limits and Micrometer reports receiver pressure.
• Journal replay applies events in bounded slices, allowing other recovery work to progress between slices.
• User documentation is separated from maintainer procedures; the documentation index links configuration, recovery, observability and integration guides.

Fixed

• Successfully committed remote writes preserve local coherence even when invalidation barriers race with local publication. Rejected writes cannot overwrite the winning value in L1.
• Cache registration waits for invalidation readiness, and dispatch overflow remains visibly pending until verified replay or conservative clear restores a safe baseline.

Validation

• Virtual-thread checks separate cold-start diagnostics from the strict steady-state gate on Java 21 and 25.
• Lock-provider shutdown tests observe the provider's owned executor termination instead of unrelated JVM thread counts.
• Six-instance tests exercised Sentinel failover, Redis outages, instance isolation and restart, Pub/Sub reconnect and source failures. Follow-up checks converged on all instances; transient stale reads during Redis failures remain possible under the documented eventual-consistency contract.

See upgrade notes and the documentation index.