Kiln —
Self-hosted feature flags with a real-time config wire.

Kiln is what feature-flag tooling should cost: less than your office snacks budget. Self-hosted by default, cloud as a convenience.

Feature-flag SaaS contracts had drifted into the five figures for teams that just needed a fast key-value flag service with audit logs. The market was begging for an open-core alternative.

We made the open-source version genuinely good — single binary, sub-10ms p99 reads, real-time WebSocket fanout — and charged for the cloud-hosted convenience tier and the audit/compliance add-ons.

11,000 self-hosted installs and a healthy $22K MRR cloud business. Featured on the front page of two large dev publications. Used by three YC companies in production.

Founder + sole engineer for the first year. Now lead one of two engineers.