Four seconds is the price of knowing the machine didn't exist before you asked for it

Most containers you create are claimed, not born. The platform keeps warm prespawn pools; a normal POST /projects/{id}/containers matches one and returns in milliseconds.

The release build is the exception. Its create carries bypass_prespawn: true. No claim: the container is provisioned inside that request, one to five seconds, and nothing about it existed before the build asked.

The reason is evidentiary. A prespawn container isn't yet bound to the server it will finally run on; a snapshot on one is refused with SNAPSHOT_PRESPAWN_FORBIDDEN until it's claimed. For a build whose artifact is a snapshot and whose provenance gets audited, you want the machine's history to begin at the request, with no warm-pool chapter before it.