Remove the fallback mechanism that queried the database when Redis keys were missing or unavailable. The `GetConvMaxSeq` and `GetConvMaxSeqBatch` methods now strictly rely on the Redis cache and return `ErrKeyNotFound` if the data is not present.
Remove the fallback mechanism that queried the database when Redis keys were missing or unavailable. The `GetConvMaxSeq` and `GetConvMaxSeqBatch` methods now strictly rely on the Redis cache and return `ErrKeyNotFound` if the data is not present.