4xx Client errors
425 Too Early
The server won't risk processing a request that might be replayed.
Common causes
- TLS 0-RTT (early data) requests.
How to fix it
- Clients retry automatically after the handshake completes.
Find out the moment your site returns 425
Spot Downtime monitors count this as down and alert you, since visitors see an error. (The public “Is it down?” checker treats 4xx answers from big sites as online, because many refuse automated requests.)