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Amazon ElastiCache
ElastiCache for Memcached User Guide (API Version 2015-02-02)

Comparing Memcached and Redis

Amazon ElastiCache supports the Memcached and Redis cache engines. Each engine provides some advantages. Use the information in this topic to help you choose the engine and version that best meets your requirements.

Important

After you create a cache cluster or replication group, you can upgrade to a newer engine version, but you cannot downgrade to an older engine version. If you want to use an older engine version, you must delete the existing cache cluster or replication group and create it again with the earlier engine version.

On the surface, the engines look similar. Each of them is an in-memory key-value store. However, in practice there are significant differences.

Choose Memcached if the following apply for you:

  • You need the simplest model possible.

  • You need to run large nodes with multiple cores or threads.

  • You need the ability to scale out and in, adding and removing nodes as demand on your system increases and decreases.

  • You need to cache objects, such as a database.

Choose Redis with a version of ElastiCache for Redis if the following apply for you:

  • ElastiCache for Redis version 4.0.10 (Enhanced)

    Supports both encryption and dynamically adding or removing shards from your Redis (cluster mode enabled) cluster.

    For more information, see Redis Version 4.0.10 (Enhanced).

  • ElastiCache for Redis version 3.2.10 (Enhanced)

    Supports the ability to dynamically add or remove shards from your Redis (cluster mode enabled) cluster.

    Important

    Currently ElastiCache for Redis 3.2.10 doesn't support encryption.

    For more information, see:

  • ElastiCache for Redis version 3.2.6 (Enhanced)

    If you need the functionality of earlier Redis versions plus the following features, choose ElastiCache for Redis 3.2.6:

  • ElastiCache for Redis (Cluster mode enabled) version 3.2.4

    If you need the functionality of Redis 2.8.x plus the following features, choose Redis 3.2.4 (clustered mode):

    • You need to partition your data across two to 15 node groups (clustered mode only).

    • You need geospatial indexing (clustered mode or non-clustered mode).

    • You don't need to support multiple databases.

    Important

    Redis (cluster mode enabled) has the following limitations:

    • No scale-up to larger node types

    • No changing the number of replicas in a node group (partition)

    Redis version 3.2.4 (cluster mode enabled) has the following limitations:

    • No dynamic scale-up to larger node types.

    • No dynamic changing the number of replicas in a node group (partition).

  • ElastiCache for Redis (non-clustered mode) 2.8x and 3.2.4 (Enhanced)

    If the following apply for you, choose Redis 2.8.x or Redis 3.2.4 (non-clustered mode):

    • You need complex data types, such as strings, hashes, lists, sets, sorted sets, and bitmaps.

    • You need to sort or rank in-memory datasets.

    • You need persistence of your key store.

    • You need to replicate your data from the primary to one or more read replicas for read intensive applications.

    • You need automatic failover if your primary node fails.

    • You need publish and subscribe (pub/sub) capabilities—to inform clients about events on the server.

    • You need backup and restore capabilities.

    • You need to support multiple databases.

Comparison summary of Memcached, Redis (cluster mode disabled), and Redis (cluster mode enabled)

Memcached Redis (cluster mode disabled) Redis (cluster mode enabled)
Engine versions 1.4.x 2.8.x and 3.2.x 3.2.x
Data types Simple ‡ 2.8.x - Complex * Complex †
3.2.x - Complex †
Data partitioning Yes No Yes
Cluster is modifiable Yes Yes No
Online resharding No No 3.2.10
Encryption No 3.2.6 3.2.6
HIPAA Compliance No 3.2.6 3.2.6
Multi-threaded Yes No No
Node type upgrade No Yes No
Engine upgrading Yes Yes No
High availability (replication) No Yes Yes
Automatic failover No Optional Required
Pub/Sub capabilities No Yes Yes
Sorted sets No Yes Yes
Backup and restore No Yes Yes
Geospatial indexing No 2.8.x - No Yes
3.2.x - Yes
Notes:
‡ string, objects (like databases)
* string, sets, sorted sets, lists, hashes, bitmaps, hyperloglog
† string, sets, sorted sets, lists, hashes, bitmaps, hyperloglog, geospatial indexes

After you choose the engine for your cluster, we recommend that you use the most recent version of that engine. For more information, see Supported ElastiCache for Memcached Versions or Supported ElastiCache for Redis Versions.