AWS Elasticache Serverless + incompatible maxmemory-policy

[subvertallchris]

Hello! In the BullMQ Elasticache docs, it remarks "Use the standard cache-nodes setup (i.e. not the serverless version, as serverless for the moment uses an incompatible maxmemory-policy)". Can someone please elaborate on this? I can't find any documentation about the max-memory policy with Serverless Elasticache.

[manast]

According to the documentation it should be possible to configure: https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/ParameterGroups.Redis.html

[subvertallchris]

Not with Elasticache Serverless. See "Configurability" here: https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/WhatIs.deployment.html#WhatIs.deployment.comparing

[manast]

Well, then I guess you answered the question yourself :)

[subvertallchris]

Sort of! I know it can’t be changed but I’m curious about what policy it uses and why it’s incompatible. My understanding of Serverless Elasticache is that it grows as needed so I wouldn’t expect “max memory” to be a thing.

[manast]

Because noeviction is the only policy that guarantees that no keys will be ever removed by Redis itself. Since this is serverless and in theory the memory increases automatically maybe it will be a de facto noeviction, but better to ask the AWS support to be sure.