Load balancers are the silent infrastructure. You don't think about them until they start dropping connections at 2 AM. Here are the settings that have bitten me in production.
Connection timeouts
Default connection idle timeout on AWS ALB is 60 seconds. Your app might have requests that legitimately take 90 seconds. Result: the ALB drops the connection mid-request, your user sees a 502, and your logs show nothing because the app was still processing.
Rule: set the LB idle timeout higher than your longest legitimate request. For most APIs, 120-300 seconds. Verify it matches your app's own timeout.
Health check intervals
