Bun

Bun is a modern JavaScript runtime built as a drop-in replacement for Node.js, written in Zig and powered by JavaScriptCore (the engine behind Safari) rather than V8. It ships as a single binary that unifies four tools developers previously stitched together: a runtime, an npm-compatible package manager, a bundler/transpiler, and a test runner. Bun natively executes TypeScript and JSX without a separate build step, implements Web-standard APIs (fetch, WebSocket, ReadableStream, FormData) alongside Node.js APIs (fs, path, Buffer, most of the node: module surface), and includes a built-in SQLite driver, Postgres/Redis clients, and a fast Bun.serve() HTTP server with native WebSocket and file-streaming support. Its primary use cases span backend API servers, CLI tooling, monorepo package management, full-stack frameworks (Next.js, Remix, Elysia, Hono), and CI test execution, where its startup time and install speed (bun install is often 10-30x faster than npm) meaningfully cut developer iteration loops and cold-start latency in serverless/edge contexts. Because it targets Node.js API compatibility, most existing Express, Fastify, and Prisma-based codebases run with minimal changes, making Bun attractive to teams migrating performance-sensitive services without a full rewrite. Bun itself is an open-source runtime (MIT licensed) rather than a hosted cloud database or PaaS, but it's frequently deployed on serverless/edge-adjacent platforms (Railway, Fly.io, Render, Vercel via custom runtimes, AWS Lambda via container images) that bill on usage, which is why it's commonly evaluated alongside cloud hosting and serverless DB tooling. Its target audience is backend/full-stack engineers and platform teams optimizing for cold-start latency, build speed, and reduced tooling sprawl in TypeScript-heavy stacks.