Redis Essentials

Optimizing with Hashes

The previous time series implementation uses one Redis key for each second, minute, hour, and day. In a scenario where an event is inserted every second, there will be 87,865 keys in Redis in a full day (assuming a day starts at 00:00:00):

• 86,400 keys for the 1sec granularity (60 * 60 * 24).
• 1,440 keys for the 1min granularity (60 * 24).
• 24 keys for the 1hour granularity (24 * 1).
• 1 key for the 1day granularity.

This is an enormous number of keys per day, and this number grows linearly over time. A large number of keys is not very good for debugging, and each key has a memory cost that comes with it. In a benchmark test that we did—in which we inserted one event per second for 24 hours (86,400 events)—Redis allocated about 11 ...