content/develop/whats-new/8-4.md
Redis 8.4 builds on the foundation of Redis 8.2 with significant enhancements to cluster operations, string manipulation, and stream processing capabilities.
This release delivers major improvements across multiple areas:
Below is a detailed breakdown of these updates.
Redis 8.4 introduces the [CLUSTER MIGRATION]({{< relref "/commands/cluster-migration/" >}}) command, which enables atomic slot migration between cluster nodes. This command ensures zero-downtime cluster operations by moving slots and their associated data in a single atomic operation, eliminating the brief unavailability window that previously occurred during slot migrations.
Redis 8.4 extends string manipulation capabilities with powerful new commands that enable atomic compare-and-set operations:
DELEX]({{< relref "/commands/delex/" >}}): Delete a key only if its value matches a specified condition.DIGEST]({{< relref "/commands/digest/" >}}): Generate cryptographic digests of key values for integrity verification.The [SET]({{< relref "/commands/set/" >}}) command now supports atomic compare-and-set and compare-and-delete operations through new extensions, enabling you to implement lock-free data structures and optimistic concurrency control patterns.
The new [MSETEX]({{< relref "/commands/msetex/" >}}) command allows you to set multiple keys and update their expiration times in a single atomic operation. This simplifies batch operations where you need to maintain consistent TTL values across related keys.
Redis 8.4 enhances stream processing with the CLAIM min-idle-time option for [XREADGROUP]({{< relref "/commands/xreadgroup/" >}}). This feature enables consumer groups to automatically claim and process both idle pending entries and new incoming entries in a single operation, simplifying consumer group management and improving processing efficiency.
The new FT.HYBRID command introduces hybrid queries that combine multiple ranking algorithms using Reciprocal Rank Fusion (RRF) and linear combination methods. This enables you to create sophisticated search experiences that leverage both semantic similarity and traditional text matching.
Redis 8.4 introduces auto-repair options for corrupted AOF (Append Only File) tails during startup. The new aof-load-corrupt-tail-max-size configuration parameter allows Redis to automatically repair minor AOF corruption, improving system resilience and reducing manual intervention requirements.
Redis 8.4 delivers substantial performance improvements through advanced SIMD optimizations and enhanced algorithms.
VADD and VSIM commands benefit from AVX2 and AVX512 dot product implementations for faster vector processing.decode_array_with_array_mt configuration parameter for better memory utilization.Redis 8.4 introduces several improvements to search functionality:
search-default-scorer parameter sets BM25STD as the default text and tag scorer, providing better relevance ranking out of the box.search-on-oom parameter controls query behavior during out-of-memory conditions, with options to ignore, fail, or return partial results.search-io-threads parameter allows you to configure communication threads for cluster manager coordination, improving search performance in clustered environments.Redis 8.4 introduces new configuration parameters that give you greater control over system behavior:
lookahead: Runtime-configurable lookahead depth for command prefetching (default: 16)aof-load-corrupt-tail-max-size: Maximum corrupted tail size for automatic AOF repairdecode_array_with_array_mt: Controls how Lua handles empty JSON arraysRedis 8.4 continues the unified distribution approach, delivering all functionality in a single Redis Open Source package without separate modules. This includes:
HELP and COMMAND DOCS support for time series commandsHELP and COMMAND DOCS support for probabilistic commandsWhen using Redis 8.4, be aware of these current limitations:
FT.SEARCH, FT.AGGREGATE, FT.CURSOR, FT.HYBRID) and time series commands (TS.MGET, TS.MRANGE, TS.MREVRANGE, TS.QUERYINDEX) may return partial results or duplicates during atomic slot migration.FT.PROFILE, FT.EXPLAIN, and FT.EXPLAINCLI don't include FT.HYBRID options.FT.HYBRID metrics aren't displayed in FT.INFO and INFO commands.FT.HYBRID options (EXPLAINSCORE, SHARD_K_RATIO, YIELD_DISTANCE_AS, WITHCURSOR) are not yet available.COMBINE step using FILTER is not currently supported.