When we moved Twilio’s million-recipient messaging system to Temporal, we thought durable execution would solve everything. Then we had our first incident and it made us rethink everything.

This talk traces the real architecture evolution: from child workflows that generated tens of thousands of Temporal actions, to long-running activities with heartbeat checkpoints, to a sliding window pattern that parallelizes work across the fleet. We’ll cover the operational gotchas that surprised us, a second service where we use entity workflows to serialize concurrent mutations, and the Temporal primitives (fairness keys, StartDelay, workflow ID dedup) that replaced custom infrastructure we thought we needed to build.

You’ll leave with patterns you can steal and the hard-won intuition for designing Temporal workflows at scale.