Sessions are currently stored in Redis, a highly-optimized in-memory store with request latency reportedly on the order of ~1 ms. Given the nature of the proposed session storage service, latency can only be higher than what we're accustomed to; It seems implied that we are striking a bargain to trade away some latency in return for multi-master replication, but have not yet agreed upon a price.
We should to establish an SLA for the proposed session storage service.
Per discussion below:
Action | Redis (ms) | Multiplier | Mean latency (ms) | p90 latency (ms) | error rate |
GET | 1 | 2 | 2 | 3 | 1% |
SET | 45 | 1 | 45 | 75 | 1% |
DELETE | 1 | 10 | 10 | 15 | 1% |