This topic describes the limits on data types and some features of ApsaraDB for Redis.

Item Description
List data type The numbers of lists and elements in a list are unlimited. The maximum size of each element is 512 MB. We recommend that the number of elements in a list is less than 8,192. The maximum value length is 1 MB.
Set data type The numbers of sets and elements in a set are unlimited. The maximum size of each element is 512 MB. We recommend that the number of elements in a set is less than 8,192. The maximum value length is 1 MB.
Sorted set data type The numbers of sorted sets and elements in a sorted set are unlimited. The maximum size of each element is 512 MB. We recommend that the number of elements in a sorted set is less than 8,192. The maximum value length is 1 MB.
Hash data type The numbers of hash tables and elements in a hash table are not limited. The maximum size of each element is 512 MB. We recommend that the number of elements in a hash table is less than 8,192. The maximum value length is 1 MB.
Number of databases (DBs) Each instance supports 256 databases.
Note
  • The total size of data stored in all databases depends on the memory size of an instance.
  • The system automatically assigns memory to a single DB based on the usage. The upper limit of assigned memory is the instance memory. For example, if DB 0 occupies all memory, other databases have no data.
Supported Redis commands For more information, see Overview.
Monitoring and alerting

ApsaraDB for Redis does not provide capacity alerts. You have to configure this feature in Cloud Monitor. For more information, see Alert settings.

We recommend that you set alerts for the following metrics: instance faults, instance failover, connection usage, failed operations, capacity usage, write bandwidth usage, and read bandwidth usage.

Policies to delete expired data
  • Active expiration: the system periodically detects and deletes expired keys in the background.
  • Passive expiration: the system deletes expired keys when you access these keys.
Idle connection recycling mechanism ApsaraDB for Redis does not automatically recycle idle connections to ApsaraDB for Redis. You can manage the connections.
Data persistence policy ApsaraDB for Redis uses the AOF_FSYNC_EVERYSEC policy and runs the fsync command at a one-second interval.