Ten seconds. That's how long your endpoint has to return a 200 OK when a Nylas webhook fires — and it's the only latency contract an email agent actually has to meet. Everything else about the workload is bursty, stateless, and event-shaped, which is a near-perfect description of what serverless platforms are built for.
Most email agents spend their lives idle. Mail arrives in bursts, the agent reasons for a few seconds, sends a reply, and goes quiet again. Running a 24/7 server for that is paying for silence. A function that wakes on a webhook and scales to zero matches the workload exactly.
The event source is already push
The reason this architecture works is that you never poll. A single subscription to the message.created trigger gets you a push the moment mail lands in any mailbox on your application:
curl --request POST \
