At Most Once
In plain terms
A delivery guarantee where messages may be lost but never duplicated.
Going deeper
At-most-once delivery sends a message without retries, so it's processed zero or one times, fast but potentially lossy. Speed over reliability.
Under the hood
Fire-and-forget; acceptable when occasional loss is fine but duplicates are not.
Examples
Metrics, logging, UDP, fire-and-forget messaging, lossy-tolerant systems.
Think of it like...
Like mailing a postcard once, it might not arrive, but you'll never send two.