This document lists the new features, enhancements, fixed issues and, removed or deprecated features for Hazelcast IMDG 4.2.1 release. The numbers in the square brackets refer to the issues in Hazelcast's GitHub repositories.

## Enhancements

* Enhanced the `getPartitionGroupStrategy()` method to have cluster members
as arguments so that useful partitioning strategies can be implemented
by accessing the members using this method. [#18904]
* The log message for infinite cluster connection timeout is clearer now.
Previously, it was represented as the value of `Long.MAX_VALUE`. [#18648]
* Introduced a new mechanism in the background expiration tasks;
now a thread local array controls the allocations for these tasks
otherwise which may cause increased garbage collection pressure and
CPU usage spikes when you use aggressive expiration configurations,
e.g., low time-to-live values. [#18507]

## Fixes

* Fixed an issue where the health monitor was incorrectly showing the
value for free metadata memory. [#18953]
* Fixed an issue where the updates made to a persistent map store might be lost
when the write coalescing is enabled. [#18929]
* Some merge policies like `LatestUpdateMergePolicy` for the map and WAN replication configurations
require the per-entry statistics to be enabled. Previously, this configuration inconsistency was causing the related member
to fail at runtime. Now, the Hazelcast member fails to start, i.e., fast fails, in such a case. [#18875]
* Fixed an issue where the maximum size policy for a map was being ignored
when the policy is `PER_NODE` and the cluster is scaled down
(due to losing or killing a member). [#18873]
* Fixed an issue where the map's Near Cache was setting its maximum size as 10.000
even if the configured eviction policy is `NONE`. [#18812]
* The LRU eviction policy now takes last access time value into account to prevent
premature removal of the lately added but not yet accessed map entries. [#18624]

## Contributors

We would like to thank the contributors from our open
source community who worked on this release:

* [Lenny Primak](https://github.com/lprimak)

