Firenook is a drop-in for Firebase emulators that keeps data between restarts

Teams that build on Firebase often skip the local emulators. They are slow to start and they lose their data every time. Firenook is a new Rust project that keeps the same firebase.json, SDKs and ports. It runs faster and keeps the data between restarts. The author posted it on Hacker News this week. The post reached 107 points and 16 comments.

Firenook 0.2.1 is open source under Apache 2.0 and installs from npm. The home page lists the version and the licence.

What it replaces

Firenook runs Firestore, Authentication, Cloud Storage, Cloud Functions, Pub/Sub, Cloud Tasks, Eventarc and Extensions on their usual ports. Node 22, 24 or 26 runs the Functions, the same way Firebase runs them in production. There is no Java and nothing else to download at install or start.

Four parts of Firebase are not emulated. The home page lists Realtime Database, Hosting, App Hosting and Data Connect. A firebase.json that configures these still starts the emulator, with a warning printed.

Firenook imports and exports the same format as the official emulator. The home page says a team can switch back with one command.

The numbers Firenook reports

The home page carries a benchmark against the official emulator. It is Firenook's own test. The author ran two hours of a production app against each emulator in turn. Every operation was timed on the client. The app held 211,205 Firestore documents and 6.7 GB in Storage. Both emulators ran on one server.

Measured on that run, the median write took 5.1 ms with Firenook and 208.2 ms with the official emulator. Peak memory was 2.11 GiB with Firenook and 22.57 GiB with the official one. A restart with data kept took 0.59 seconds against 30.8 seconds. The CPU used over two hours was 616 seconds against the official emulator's 1,586 seconds. The median listener update was 11 ms against 209 ms. An orderBy limit 20 query took 12 ms against 96.3 ms. The post says Firenook answered 25 of 26 query shapes faster and tied on the last one.

These are the author's measurements. No outside team has repeated them.

What a Firebase team would check

The home page says every release passes conformance replays against the official emulator. Packed installs are tested on macOS, Linux and Windows. Version 0.2.0 is called the first release for public use. Firenook is not made by Google.

A team should try this against its own Firestore rules, its own Functions and its own Pub/Sub triggers. The repository and the release notes are on GitHub. The npm package is firenook. The project had 34 stars on GitHub when the Show HN post landed.

Source

• Primary source: Firenook: A faster drop-in for the Firebase emulators, by the Firenook project, Apache 2.0.
• Discovery: Show HN post for Firenook on Hacker News, 107 points.
• Repository: firenook-dev/firenook on GitHub.