Valkey and Redis OSS configuration and limits

The Valkey and Redis OSS engines each provides a number of configuration parameters, some of which are modifiable in ElastiCache for Redis OSS and some of which are not modifiable to provide stable performance and reliability.

Serverless caches

For serverless caches, parameter groups are not used and all Valkey or Redis OSS configuration is not modifiable. The following Valkey or Redis OSS parameters are in place:

Name	Details	Description
acl-pubsub-default	allchannels	Default pubsub channel permissions for ACL users on the cache.
client-output-buffer-limit	normal 0 0 0 pubsub 32mb 8mb 60	Normal clients have no buffer limit. PUB/SUB clients will be disconnected if they breach 32MiB backlog, or breach 8MiB backlog for 60s.
client-query-buffer-limit	1 GiB	The maximum size of a single client query buffer. Additionally, clients cannot issue a request with more than 3,999 arguments.
cluster-allow-pubsubshard-when-down	yes	This allows the cache to serve pubsub traffic while the cache is partially down.
cluster-allow-reads-when-down	yes	This allows the cache to serve read traffic while the cache is partially down.
cluster-enabled	yes	All serverless caches are cluster mode enabled, which allows them to transparently partition their data across multiple backend shards. All slots are surfaced to clients as being owned by a single virtual node.
cluster-require-full-coverage	no	When the keyspace is partially down (i.e. at least one hash slot is inaccessible), the cache will continue accepting queries for the part of the keyspace that is still covered. The entire keyspace will always be "covered" by a single virtual node in cluster slots.
lua-time-limit	5000	The maximum execution time for a Lua script, in milliseconds, before ElastiCache takes action to stop the script. If lua-time-limit is exceeded, all Valkey or Redis OSS commands may return an error of the form ____-BUSY. Since this state can cause interference with many essential Valkey or Redis OSS operations, ElastiCache will first issue a SCRIPT KILL command. If this is unsuccessful, ElastiCache will forcibly restart Valkey or Redis OSS.
maxclients	65000	The maximum number of clients that can be connected to the cache at one time. Further connections established may or may not succeed.
maxmemory-policy	volatile-lru	Items with a TTL set are evicted following least-recently-used (LRU) estimation when a cache's memory limit is reached.
notify-keyspace-events	(an empty string)	Keyspace events are currently not supported on serverless caches.
port	Primary port: 6379 Read port: 6380	Serverless caches advertise two ports with the same hostname. The primary port allows writes and reads, whereas the read port allows lower-latency eventually-consistent reads using the READONLY command.
proto-max-bulk-len	512 MiB	The maximum size of a single element request.
timeout	0	Clients are not forcibly disconnected at a specific idle time, but they may be disconnected during steady-state for load balancing purposes.

Additionally, the following limits are in place:

Name	Details	Description
Size per cache	5,000 GiB	Maximum amount of data that can be stored per serverless cache.
Size per slot	32 GiB	The maximum size of a single Valkey or Redis OSS hash slot. Clients trying to set more data than this on a single Valkey or Redis OSS slot will trigger the eviction policy on the slot, and if no keys are evictable, will receive an out of memory (OOM) error.
ECPU per cache	15,000,000 ECPU/second	ElastiCache Processing Units (ECPU) metric. The number of ECPUs consumed by your requests depends on the vCPU time taken and the amount of data transferred.
ECPU per slot	30K - 90K ECPU/second	Maximum of 30K ECPUs/second per slot or 90K ECPUs/second when using Read from Replica using READONLY connections.
Arguments per Request	3,999	Maximum number of arguments per request. Clients sending more arguments per request will receive an error.
Key name length	4 KiB	The maximum size for a single Valkey or Redis OSS key or channel name. Clients referencing keys larger than this will receive an error.
Lua script size	4 MiB	The maximum size of a single Valkey or Redis OSS Lua script. Attempts to load a Lua script larger than this will receive an error.

Self-designed clusters

For self-designed clusters, see Valkey and Redis OSS parameters for the default values of configuration parameters and which are configurable. The default values are generally recommended unless you have a specific use case requiring them to be overridden.