During peak hours, Salesforce is processing far more concurrent transactions. API calls compete with user activity, automation, and background jobs for shared resources. This makes timeouts and lock contention more likely.
Synchronous integrations are especially sensitive to this because they wait for immediate responses. When Salesforce is under load, even efficient requests may exceed timeout thresholds.
Most teams address this by using asynchronous patterns, batching updates, and designing retry logic that respects system load.
Takeaway: Integration reliability depends as much on timing and load as on code quality.