Provisioning a mailbox in nine seconds

The budget

Nine seconds, end to end, from submitted form to a mailbox that can receive mail. Here is where the time goes.

Validation first

We reject impossible addresses before touching the database:

const ADDRESS = /^[a-z0-9]([a-z0-9._-]{1,28})[a-z0-9]$/;

export function isValidLocalPart(value: string) {
  return ADDRESS.test(value.toLowerCase());
}

The slow part is DNS

Six of the nine seconds are spent waiting for the world to agree that a subdomain exists. We hide that latency by optimistically rendering the mailbox and streaming its status.

Failure is a first-class state

Every provisioning attempt writes a queue row. If the provider handshake fails we retry with backoff and surface the attempt count in the dashboard rather than silently dropping it.

Measuring it

p50 is 8.4 s, p95 is 11.2 s. We track both on the monitoring page and alert when p95 crosses fifteen seconds.