Node and edge
Runs in Workers, Lambda and Deno with zero cold-start cost.
Feature flags · v4.2
Ship on Friday. Flip it off on Saturday.
Kestrel puts every release behind a flag, evaluates it in 4 ms at the edge, and rolls it back without a deploy.
// checkout.ts
import { flag } from "@kestrel/edge";
if (await flag("new-checkout", user)) {
return renderCheckoutV2();
}
// 38% of EU traffic · p95 4.1 ms
02 · SDKs
Nine SDKs. One flag file.
TS
GO
Go
A 600-line client with no dependencies outside the standard library.
PY
Python
Async and sync clients, typed, with a pytest fixture.
RB
Ruby
A Rails engine that adds flags to your admin in one line.
03 · Pricing
Free until it matters.
HOBBY
$0
5 seats, 1 million evaluations a month.
TEAM
$12
Per seat a month. Audit log, approvals, SSO.
04 · Changelog
What changed this month.
- 4.2: edge evaluation in 11 regions, p95 under 5 ms.
- Scheduled rollouts now accept a timezone per rule.
- The Ruby SDK reaches 2.0 with Rails 8 support.
05 · Customers
2,400 teams flip flags here.
Fieldnote
"We rolled back a broken payment flow in 9 seconds, on a Sunday."
Orrin Freight
"Every route change ships to 1% of drivers first."