Show HN: Firenook – Firebase emulators in Rust: 40× faster writes, 10× less RAM

2026-11-05T13:07:29+00:00

A faster drop-in replacement for the Firebase Local Emulator Suite

Keep your firebase.json, SDKs and ports, and change one word in your script. No Java to install, and your data survives restarts.

40×

faster writes 5.1 ms against 208.2 ms, median

10×

less memory 2.11 GiB against 22.57 GiB at peak

0.59 s

to restart with your data against 30.8 s

  ╭──────────────────────────────────────────────────────────────────────────────────────────────────────╮
  │                                                                                                      │
  │       ▄█                                                                                             │
  │    ▄███▀ ▄     firenook  0.2.0                                                                       │
  │  ▄███▀ ███▄    demo-shop · picking up the data saved just now                                        │
  │  ▀██▀ ███▀     Node 24.20.0 · data in .firenook/state                                                │
  │      █▀▀                                                                                             │
  │                                                                                                      │
  ├─ Start-up ────────────────────────────────────────────────────────────────────────────────── 796 ms ─┤
  │                                                                                                      │
  │  Firestore   ✓ 255 ms  1,207,802 documents                                                           │
  │  Auth        ✓ 255 ms  64,000 users                                                                  │
  │  Storage     ✓ 255 ms  5,400 objects                                                                 │
  │  Functions   ✓ 423 ms  4 functions                                                                   │
  │  Pub/Sub     ✓   0 ms  1 schedule                                                                    │
  │                                                                                                      │
  ├─ ✓ All emulators ready ──────────────────────────────────────────────────────────────────────────────┤
  │                                                                                                      │
  │  Console       http://127.0.0.1:4000/console                                                         │
  │  Ports         Firestore 8080   Auth 9099   Storage 9199   Functions 5001   Pub/Sub 8085   Hub 4400  │
  │                                                                                                      │
  ╰──────────────────────────────────────────────────────────────────────────────────────────────────────╯

  ── Logs ────────────────────────────────────────────────────────────────────────────────────────────────

     21:05:40    ✓ checkout        117 ms  http · POST / · 201
     21:05:40    ✓ sendReceipt       6 ms  firestore · orders/qXoV1oOgJ0IILQs5psZP created
                 │ receipt queued   order qXoV1oOgJ0IILQs5psZP · total 36
     21:05:42    ✓ checkout          4 ms  http · POST / · 201
     21:05:42    ✓ sendReceipt       1 ms  firestore · orders/ZskDC6u3kTKSGalf4o5L created
                 │ receipt queued   order ZskDC6u3kTKSGalf4o5L · total 32
     21:05:43    ✕ stripeWebhook     1 ms  http · POST / · 500
                 │ Unhandled error Error: No signatures found matching the expected signature for payload
                 │   at functions/index.js:24:11
                 │ + 9 more lines · open in console


  ────────────────────────────────────────────────────────────────────────────────────────────────────────
     ● running 6s · 5 calls · 1 failed                              o console   r reload   ? keys   q quit

  ╭────────────────────────────────────────────────────────────╮
  │                                                            │
  │       ▄█                                                   │
  │    ▄███▀ ▄     firenook  0.2.0                             │
  │  ▄███▀ ███▄    demo-shop · picking up the data saved jus…  │
  │  ▀██▀ ███▀     Node 24.20.0 · data in .firenook/state      │
  │      █▀▀                                                   │
  │                                                            │
  ├─ Start-up ──────────────────────────────────────── 602 ms ─┤
  │                                                            │
  │  Firestore   ✓ 240 ms  1,207,804 documents                 │
  │  Auth        ✓ 240 ms  64,000 users                        │
  │  Storage     ✓ 240 ms  5,400 objects                       │
  │  Functions   ✓ 299 ms  4 functions                         │
  │  Pub/Sub     ✓   0 ms  1 schedule                          │
  │                                                            │
  ├─ ✓ All emulators ready ────────────────────────────────────┤
  │                                                            │
  │  Console       http://127.0.0.1:4000/console               │
  │  Ports         Firestore 8080   Auth 9099   Storage 9199   │
  │                Functions 5001   Pub/Sub 8085   Hub 4400    │
  │                                                            │
  ╰────────────────────────────────────────────────────────────╯

  ── Logs ──────────────────────────────────────────────────────

     21:05:49    ✓ checkout        115 ms  http · POST / · 201
     21:05:49    ✓ sendReceipt       6 ms  firestore · orders/E…
                 │ receipt queued
                 │ order EYi9LKG7xQ53eLrWktHm · total 36
     21:05:50    ✓ checkout          6 ms  http · POST / · 201
     21:05:50    ✓ sendReceipt       2 ms  firestore · orders/C…
                 │ receipt queued
                 │ order CU0LwsLgczq054BqsEuH · total 32
     21:05:51    ✕ stripeWebhook     1 ms  http · POST / · 500
                 │ Unhandled error Error: No signatures found
                 │ matching the expected signature for payload
                 │   at functions/index.js:24:11
                 │ + 9 more lines · open in console


  ──────────────────────────────────────────────────────────────
     ● running 6s · 5 calls · 1 failed
     o console   r reload   ? keys   q quit

$ npx firebase emulators:start

Firenook’s own screen, recorded from 0.2.0 on a demo shop: it starts with the 1.2 million documents, 64,000 users and 5,400 files it kept from its last run, takes two orders, and shows a webhook that fails, with its stack trace.

Change one word

Same flags, same ports, same export format. Your project stays as it is, and firebase-tools stays for deploying.

package.json

-  "emulators": "firebase emulators:start --import ./data"+  "emulators": "firenook emulators:start --import ./data"

firebase.json and .firebaserc

Read the way the Firebase CLI reads them.
Rules, indexes, Functions

Your code and config stay as they are.
Your SDKs

connectFirestoreEmulator, FIRESTORE_EMULATOR_HOST and the rest connect unchanged.
Your data

Imports and exports the official format, both ways.

Eight emulators, on the ports you already use

Your SDKs connect to them as they connect to Google’s: the same hosts, the same ports, the same environment variables.

Firestore

8080

Native and web SDKs, realtime listeners, Security Rules, named databases, and the official import and export.

orders 12 documents

XXfs8ZLaWvmMOeaVAcw8
5XSNbW90qkxiTbqQilu1
mqr7wc5Vjb6d5y75tfKy
ijO11GokICQ0ki9Ta4p9
c0yT9Jkt9NGpiX7HMV9r

createdAt

2026-10-23 13:06:17.872 UTC

items

[{ price: 54, qty: 1, sku: "hoodie" }, { price: 28, qty: 1, sku: "tee" }]

total

Authentication

9099

Every operation of the official Auth emulator: password, email link, phone, MFA, passkeys, tenants and blocking functions.

Users 12

Amara Abara amara@example.com password
Elif Demir elif@example.com password
Ines Duarte ines@example.com password

Cloud Storage

9199

The Firebase and Cloud Storage APIs, with Security Rules evaluated natively, firestore.get() included.

demo-shop.appspot.com / products 8 files

cap.svg image/svg+xml 404 B
hoodie.svg image/svg+xml 408 B
mug.svg image/svg+xml 404 B

Cloud Functions

5001

HTTP, callable and streaming functions, and every trigger: Firestore, Storage, Auth, Pub/Sub, Eventarc, schedules and task queues. Code reloads on save.

Function calls 25

Time	Function	Trigger	Summary	Status	Duration
13:06:19	stripeWebhook	http	POST /	500	1.1 ms
13:06:18	sendReceipt	firestore	orders/mzbnHY1n79leG5ioi2nD created	200	1.8 ms
13:06:18	checkout	http	POST /	201	6.3 ms
13:06:18	sendReceipt	firestore	orders/c0yT9Jkt9NGpiX7HMV9r created	200	1.7 ms
13:06:18	checkout	http	POST /	201	5.0 ms

Pub/Sub

8085

Every RPC over gRPC and HTTP/JSON: push, ordering, filters, dead-letter topics, seek, snapshots and schemas.

nightlyReport, every day 02:00: next run 2026-10-24 02:00 UTC

Cloud Tasks

9499

Queues for onTaskDispatched, with the official retry and rate-limit behaviour.

Eventarc

9299

616 s

The app holds 211,205 Firestore documents and 6.7 GB in Storage; both emulators ran on one server. Firenook answered 25 of 26 query shapes faster and tied on the last. How it was measured.

Your data stays where you left it

Add --keep-data and Firestore, Auth and Storage come back with all your data in about half a second, even with millions of documents. No export at every stop, no import at every start.

A crash loses at most the last second of writes, where the official emulator loses everything since its last export. A stop always closes the data cleanly.

npx firenook emulators:start --keep-data

Official emulator

Stop: export, 50–57 s Start: import, 21.6–23.6 s

Firenook

Stop, 0.04–0.30 s Start, 0.54–0.57 s

Stopping with the data saved, then starting again with it, on one time scale. The dim blocks are the spread between the fastest and the slowest runs.

$ npx firenook emulators:exec "node --test checkout.test.mjs"
firenook: Starting emulators: auth, functions, firestore, pubsub, storagefirenook functions: Loaded functions definitions from source: checkout, sendReceipt, stripeWebhook, nightlyReport.All emulators ready✔ checkout takes an order (173.227708ms)ℹ pass 1ℹ fail 0firenook suite stopped cleanly

exit 0 1.39 s from start to stop, the test included

A run of the demo project’s test through firenook emulators:exec on firenook 0.2.0, with some lines left out.

Run your tests against it

emulators:exec starts the suite, runs your command once everything is ready, with the emulator variables set, then stops and passes on the exit code.

CI gets plain lines, the same ones the official emulator prints, and there is no Java to set up first. Firenook needs only Node 24.

npx firenook emulators:exec "npm test"

The console the Firebase emulators should have had

Google’s Emulator UI has no page for your Functions, Pub/Sub, Cloud Tasks or Eventarc, only a log. Firenook’s console covers every service it runs, live, on the Emulator UI’s port.

Every call, with what triggered it, its outcome, its duration and its logs.

Light and dark, works offline, sends nothing anywhere. Bookmarks to the official UI’s pages open the matching console page. Every page of the console.

Give your agent the emulator, not production

firenook mcp gives a coding agent 54 tools over the running suite. It reads the log and each function call with its error, asks the Security Rules why a request is denied, and works with your data. Nothing leaves your machine.

npx firenook mcp add

Sets it up for Claude Code, Cursor and VS Code in the project’s own files. Other agents run npx firenook mcp. How agents use it.

You

The Stripe webhook answers 500 on my machine. Why?
functions_list_calls outcome: "failed"

failed

500 stripeWebhook http POST /, 1.15 ms at 13:06:19
functions_get_call id: "e72ca3-25"

error

Error: No signatures found matching the expected signature for payload

at

functions/index.js:24:11

headers

host, connection, content-type, accept, accept-language, sec-fetch-mode, user-agent, accept-encoding, content-length

body

{"type":"checkout.session.completed"}
rules_evaluate service: "storage", method: "create", path: "products/mug.svg"

verdict

deny as unauthenticated

line 9

allow read, write: if false;

The question is an example. The tool calls and their answers are from a run of the demo project on firenook 0.2.0, as Firenook gave them.

Firestore

Read, query, count, write and delete documents

Authentication

Manage users, read sign-in codes, mint ID tokens, set claims

Storage

List, read, upload, copy, move and delete files

Functions and logs

Invoke a function, read each call and the log, replay a call after a fix

Security Rules

Ask why a request is denied, test a draft, list denials

Pub/Sub, Tasks, Eventarc

Publish, peek, run tasks and schedules now, replay events

Do I still need firebase-tools?

Yes, for deploying and everything else the Firebase CLI does. Firenook replaces only the emulators: install it next to firebase-tools and run your emulators with it.

Does Firenook need Java?

No. Its services are native code in one npm package, with an engine for macOS, Linux and Windows, and nothing else is downloaded at install or start. Node 22, 24 or 26 runs your Functions, as it does in production.

Can I go back to the official emulator?

Yes. Firenook imports and exports the official format. While Firenook runs, export with npx firenook emulators:export ./export, then start the official emulator with --import ./export.

Which services does it emulate?

Firestore, Authentication, Cloud Storage, Cloud Functions, Extensions, Pub/Sub, Cloud Tasks and Eventarc. Realtime Database, Hosting, App Hosting and Data Connect are not emulated; a firebase.json that configures them still starts, with a warning.

Is it ready for my team?

0.2.0 is the first release for public use. Every release passes conformance replays against the official emulator and packed installs on all five platforms, and Firenook passed a two-hour benchmark against the official emulator on a real application. Commit your lockfile and upgrade on purpose.

Is it free?

Yes. Firenook is open source under the Apache License 2.0.

Is Firenook made by Google?

No. Firenook is an independent open-source project, not affiliated with or endorsed by Google. Firebase is a trademark of Google LLC.

Switch in three steps

One package, nothing else to install: Node 22, 24 or 26 on macOS, Linux with glibc 2.28 or newer, or Windows x64. Starting a new project instead? npx firenook init sets one up.

Install it next to firebase-tools

Keep firebase-tools for deploying: Firenook has no deploy or login command.

npm install --save-dev firenook
Check your project

This reads firebase.json the way the Firebase CLI does, and changes nothing.

npx firenook init --adopt --dry-run
Swap the command

Same flags and ports, so your app connects as before and your data imports as it is.

npx firenook emulators:start

firenook.dev

Show HN: Firenook – Firebase emulators in Rust: 40× faster writes, 10× less RAM

A faster drop-in replacement for the Firebase Local Emulator Suite

Change one word

firebase.json and .firebaserc

Rules, indexes, Functions

Your SDKs

Your data

Eight emulators, on the ports you already use

Measured on a real application

Memory at peak

Write, median

Listener update, median

Restart with data kept

orderBy, limit 20

CPU over two hours

Your data stays where you left it

Run your tests against it

The console the Firebase emulators should have had

Give your agent the emulator, not production

Switch in three steps

Install it next to firebase-tools

Check your project

Swap the command