Eliminating Cold Starts 2: Shard And Conquer
Cloudflare, Friday, September 26th, 2025
Five years ago, we announced that we were Eliminating Cold Starts with Cloudflare Workers. In that episode, we introduced a technique to pre-warm Workers during the TLS handshake of their first request.
That technique takes advantage of the fact that the TLS Server Name Indication (SNI) is sent in the very first message of the TLS handshake. Armed with that SNI, we often have enough information to pre-warm the request's target Worker.