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2026-05-24 - Redis resilience against Upstash idle disconnects

Problem​

In production, AuthService.getProfile was returning User profile not found (404) for users whose profiles existed. Logs showed the underlying error: RedisError [ERR_REDIS_CONNECTION_CLOSED]: Connection has failed. Two issues stacked:

  1. Upstash closes idle TCP connections after a few minutes. Bun's RedisClient reconnects, but commands in-flight when the socket drops (or arriving during the reconnect window) fail immediately with ERR_REDIS_CONNECTION_CLOSED. This is unlike ioredis, which queues commands during reconnects and hid the issue.
  2. getProfile's catch block converted any thrown error into NotFoundException, so Redis failures masqueraded as missing profiles.

Fix​

  • CacheService now swallows all store errors. A Redis outage degrades to "always miss, never write" instead of throwing - reads fall through to Supabase, writes silently skip.
    • get / update on store error → log + treat as cache miss (return null / false).
    • set / delete / deleteByPrefix / clear on store error → log + no-op.
  • RedisStore sends a PING every 60s to prevent Upstash from closing the socket, and is constructed with autoReconnect: true, maxRetries: 20, idleTimeout: 0.
  • CacheService implements OnModuleDestroy to tear down the keepalive interval and close the Redis socket on shutdown.
  • AuthService.getProfile no longer wraps non-domain errors. Only Supabase row-not-found produces NotFoundException; everything else surfaces as a real 500.

Operational notes​

  • REDIS_URL must use rediss:// (TLS) for Upstash.
  • Watch logs for sustained Redis keepalive ping failed warnings - sporadic ones during reconnect are expected, sustained failures indicate credentials/URL/network issues.
  • If ERR_REDIS_CONNECTION_CLOSED continues to appear after this fix, consider migrating RedisStore to @upstash/redis (HTTPS, no persistent socket). The CacheInterface abstraction makes this a single-file change.

See the Cache module docs for the full architecture and the Resilience section for the error-handling contract.