Increase default Redis maxmemory to be higher than 100MiB

[seanhamlin]

By default a redis pod will spawn with a very conservative amount of RAM that can be used. Sure it can be extended with an environment variable, but we are seeing multiple people running 100MiB in production, and experiencing extremely poor cache hit rates (I have seen as low as 14%). This metric is also not very visible to application developers (requires redis-cli commands in the container).

Suggestion

Increase the default Redis maxmemory to 400MiB.

maxmemory ${MAXMEMORY:-400mb}

400MiB was chosen as this is 4x the current limit.