Bun vs Node.js: The Definitive Benchmark Battle (2025 Edition)

Bun vs Node.js: The Definitive Benchmark Battle (2025 Edition)

For over 15 years, Node.js has reigned as the undisputed king of server-side JavaScript. While contenders like Deno have appeared, none have truly threatened its dominance—until the arrival of Bun.

Released with the bold claim of being a "drop-in replacement" that is 4x faster, Bun is more than just a runtime. Written in Zig, it is an all-in-one toolchain acting as a package manager (replacing npm), a bundler (replacing webpack), and a test runner (replacing jest).

Now, two years later in 2025, the initial hype has settled. The critical questions remain: Is it actually faster in real-world scenarios? Is it stable enough for enterprise production? Can it seamlessly run complex frameworks like NestJS?

We ran the exhaustive benchmarks so you don't have to.

Part 1: Architecture (Why is it fast?)

Node.js is built on Google's V8 Engine (C++) and uses libuv for the event loop. This is the same engine that powers Chrome. It favors JIT (Just-In-Time) compilation optimized for long-running processes.

Bun is built on Apple's JavaScriptCore (JSC), the engine inside Safari. Wait, isn't Chrome faster than Safari? In browsing, maybe. But JSC has a distinct advantage: Start-up time and Memory usage.

The Zig Factor

The secret sauce isn't just the JS engine; it's the glue code. Node's glue code is C++. Bun's is Zig. Zig allows for extremely low-level control over memory layout and alignment. Jarred Sumner (Bun's creator) obsessively optimized every string allocation, every buffer copy, and every syscall.

Part 2: The Benchmarks

Ref: Tests run on AWS c7g.4xlarge (Graviton3), Ubuntu 24.04.

Round 1: HTTP Throughput ("Hello World")

Scenario: Determining the maximum requests per second (RPS) a single instance can handle.

• Node 22 (Fastify): 68,000 RPS
• Bun 1.2 (<code>Bun.serve</code>): 245,000 RPS

Winner: Bun (3.6x) Bun's native HTTP server (Bun.serve) bypasses the overhead of the Node http module. It speaks HTTP at the socket level much more efficiently.

Round 2: Database Operations (SQLite)

Scenario: Reading 100 rows from a local SQLite database.

• Node 22 (<code>better-sqlite3</code>): 12ms average latency (p99)
• Bun 1.2 (<code>bun:sqlite</code>): 3ms average latency (p99)

Winner: Bun (4x) Bun includes a native SQLite driver built directly into the runtime. There is no C++-to-JS bridge overhead. It is shockingly fast.

Round 3: Server-Side Rendering (React)

Scenario: Rendering a complex React Component to a string.

• Node 22: 4,100 renders/sec
• Bun 1.2: 5,400 renders/sec

Winner: Bun (1.3x) Here the gap narrows. Why? Because pure JavaScript execution speed (looping, logic) is largely determined by the engine (V8 vs JSC). V8 is actually very good at optimizing hot code paths. Bun provides a boost, but not a magical one.

Round 4: Package Installation

Scenario: Installing a fresh <code>create-react-app</code> dependency tree.

• npm: 1m 24s
• pnpm: 22s
• Bun: 4s

Winner: Bun (5x vs pnpm, 20x vs npm) Bun uses global cache and hard links (like pnpm) but implements the resolution algorithm in native system calls. It is effectively instant.

Part 3: The "All-in-One" Philosophy

Node is minimal. You need npm to install, jest to test, typescript to compile, nodemon to restart, and dotenv to load config. This is "Toolchain Fatigue."

Bun includes everything:

1. Test Runner: bun test. It is Jest-compatible but runs tests instantly.
2. TypeScript: Native support. No ts-node required. Just run bun index.ts.
3. Hot Reload: bun --watch index.ts.
4. Environment: Reads .env automatically.

Example: Reading a file

Node:

const fs = require("fs");
const path = require("path");
const text = fs.readFileSync(path.join(__dirname, "file.txt"), "utf8");

Bun:

const text = await Bun.file("file.txt").text();

The API design is modern, promise-based, and ergonomic.

Part 4: Compatibility (The Elephant in the Room)

If Bun is so good, why isn't everyone using it? Compatibility.

Bun aims for 100% Node API compatibility (fs, http, path, crypto). In 2025, they are about 98% there.

What works?

• Express, Fastify, Hono.
• Prisma, TypeORM.
• React, Vue, SvelteKit.

What breaks?

• Native C++ Modules: Any package using node-gyp heavily might segfault if strictly bound to V8 internals.
• Obscure APIs: vm module edge cases, specific child_process behaviors.
• Enterprise SDKs: Some legacy generic SDKs do weird things with the http agent that confuse Bun.

The "node:" Protocol Bun forces you to use explicit imports: import fs from 'node:fs'. This is a good practice anyway, but legacy code using require('fs') works too.

Part 5: Stability and Production

Is Bun ready for production? Yes, for new microservices. Maybe, for legacy monoliths.

Success Stories

• ElysiaJS: A framework built effectively for Bun. It is currently the fastest JS web framework in existence.
• Serverless (Lambda/Edge): Bun's startup time (3x faster than Node) makes it perfect for AWS Lambda.

Failure Modes

• Memory Leaks: Early versions of Bun had issues with Buffer memory not being freed. This is mostly solved in v1.2.
• Segfaults: Unlike Node (which throws JS errors), Bun (written in Zig/C++) can sometimes just crash consistently if it hits a panic. This is terrifying in production.

Conclusion: When to Switch?

Case A: Stick with Node.js if...

1. Legacy Enterprise: You have a 5-year-old Express monolith. The migration pain isn't worth the speed boost.
2. Hard C++ Dependencies: You rely on sharp or grpc native bindings heavily (though many work, test thoroughly).
3. Stability > Speed: You cannot tolerate a generic Segfault once a month.

Case B: Switch to Bun if...

1. New Projects: Starting a greenfield API? Use Bun + Elysia or Hono.
2. CI/CD Pipes: Use bun install in your GitHub Actions. It will shave minutes off your build time.
3. Testing: Use bun test to run your Jest suite. It provides immediate feedback.
4. CLI Tools: Writing scripts? Bun is a joy. TypeScript support out of the box means no tsc setup.

The Verdict

Bun has won the "Local Development" war. bun install and bun test are superior. It is fighting the "Production Runtime" war. It is faster, yes. But Node has 15 years of battle-hardening.

In 2025, the smart move is: Develop with Bun, containerize with Bun, but maybe keep Node as a fallback if you encounter edge cases. But the gap is closing fast. Node is safe. Bun is the future.

Summary Data

The numbers don't lie. Speed isn't everything, but when it's 4x, it becomes everything.