2025
Katelyn Lesse says that when she joined Anthropic, the Messages API was a Python monolith running in a single GCP region.
“we had the Messages API. It was a Python monolith. We were running it in a, you know, single GCP region”
Topic
Messages API
5 facts from 1 episode, in date order. These are what speakers said on the shows, each linked to the moment it was said. They aren't independently verified.
2026
Anthropic built a full Rust fork of its Messages API and ran shadow traffic through it to compare outputs with the Python version.
“we literally built, like, an entire fork of the entire API in Rust, and then started running shadow traffic through it”
2026
Katelyn Lesse says the Rust rewrite of the Messages API saved roughly 40 to 50% of CPU.
“somewhere like 40 to 50%, something like really crazy”
2026
Katelyn Lesse says the Rust rewrite improved time to first token by roughly 10 to 20%.
“somewhere between like 10 and 20%, um, improvement on like time to first token specifically”
2026
Katelyn Lesse says Claude Managed Agents is a suite of APIs above the Messages API, which provides raw token access.
“Claude managed agents is our API today. We have the Messages API, which is essentially raw token access.”
Episodes