Summary
After an idle period, the first request through the built-in proxy fails (set or get) with SERVER_ERROR backend failure. Subsequent requests succeed.

Example

$ telnet <host> 11211
set a 0 0 4
test
SERVER_ERROR backend failure

Expected
No error after idle; the first request should behave like subsequent ones.

Actual
First post-idle request returns:

SERVER_ERROR backend failure

Repro

1. Start memcached with the built-in proxy.
2. Let it sit idle for N minutes.
3. Send any request → first one fails; later ones succeed.

Notes / Workaround
mcrouter mitigates similar cases via health-check/TKO:
https://github.com/facebook/mcrouter/wiki/Command-line-options#health-check

Environment

• memcached version: 1.6.39
• OS/Kernel: alpine3.22