## Context
`twenty_event_streams_live_total` (an observable gauge) calls
`getTotalActiveStreamCount()` →
`scanAndCountSetMembers('workspace:*:activeStreams')`, which runs a
full-keyspace `SCAN MATCH` over the entire Redis DB **on every metrics
scrape, on every pod**. `SCAN MATCH` walks every key (filtering only the
output), and the subscriptions namespace shares the node with the
workspace metadata cache (~190k keys in our prod), so this was the
dominant Redis command (billions of `SCAN` calls) to count a handful of
sets.
## What this does
Cache the count and refresh it via the scan at most once per
`ACTIVE_STREAM_COUNT_REFRESH_MS` (5 min) per pod, instead of on every
scrape. Steady-state scrapes return the cached value; the authoritative
scan still runs periodically so the gauge stays fresh.
Single-method change; no new Redis keys, no data-model changes.
Charles Bochet
4dd9253d01