hidane
A single Rust binary that replaces the Firestore emulator — no JVM, starts in milliseconds.
hidane replaces Google's official Firestore emulator with one Rust binary — no JVM required, where firebase-tools 15 now needs Java 21 just to run the official one. In the project's own benchmark it starts in 1.53ms using 9.3MiB idle, against 852ms and 148MiB for the official emulator, and batch writes stay flat per batch instead of slowing down 11x at 100k documents like the original. Compatibility is tested, not just claimed: 30,872 of the official emulator's answers are recorded and replayed against hidane in CI, with 26 identical results and 18 documented differences so far. Some clients — iOS, Android, and Flutter's mobile/desktop gRPC path — aren't verified yet, so compatibility there is untested rather than confirmed.
What holds up
- +No JVM needed — skips the Java 21 requirement firebase-tools 15 now forces on the official emulator.
- +1.53ms startup and 9.3MiB idle in its own benchmark, versus 852ms and 148MiB for the official emulator.
- +Compatibility is proven by replaying 30,872 recorded answers in CI, not just asserted.
- +Batch writes stay flat per batch instead of the official emulator's 11x slowdown at 100k documents.
Mind the limits
- −iOS, Android, and Flutter's mobile/desktop gRPC clients aren't verified yet — risky if that's your stack.
- −18 documented differences from the official emulator remain, even where both are compared in full.
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