What it feels like
Session locking issues often appear as intermittent slowness, stuck checkout activity, or requests that queue behind earlier requests from the same user session. The symptoms can look like general server load until you inspect timing and request patterns.
What to inspect
Review Redis latency, PHP request duration, checkout routes, concurrent AJAX calls, and session configuration. Avoid changing lock settings blindly without understanding the user journey and data consistency risk.
How to move safely
Create a test case, measure before and after, and coordinate with application developers. Infrastructure changes can reduce pressure, but application behavior still matters.