Next.js API Routes vs Elysia for Solo Developers

Quick Comparison

Next.js API Routes Overview

Next.js API Routes give you backend endpoints inside your Next.js project. File-based routing, serverless deployment on Vercel, and zero configuration to get started. If your project is already Next.js, adding a few API endpoints requires almost no effort.

I've used this approach for projects where the backend is simple. A payment webhook, a newsletter signup endpoint, a data proxy. For those use cases, API Routes are great. You stay in one project, one deployment, one mental model.

The problems show up when your API grows. There's no structured validation, no type-safe request/response pipeline, and no built-in middleware beyond what Next.js provides at the edge. You end up writing a lot of boilerplate to handle things that a dedicated framework gives you for free.

Elysia Overview

Elysia is what happens when you design a web framework specifically for Bun from the ground up. It's fast, type-safe, and has an ergonomic API that feels genuinely modern. The end-to-end type safety is the standout feature. Your route parameters, request body, response shape, and validation are all connected through TypeScript inference.

When I first tried Elysia, the type safety clicked immediately. You define your schema once and TypeScript knows the types everywhere. No manual type assertions, no runtime type mismatches. The t.Object() schema system validates requests AND infers types at the same time. That's a developer experience improvement that actually saves debugging time.

Performance-wise, Elysia on Bun is exceptionally fast. Benchmarks put it among the fastest JavaScript frameworks available, sometimes matching Go or Rust frameworks for simple workloads. Whether that matters for your project depends on your scale, but it's nice to know performance won't be your bottleneck.

Key Differences

Type safety is where Elysia shines. Next.js API Routes use TypeScript, but there's no connection between your validation logic and your TypeScript types. You validate with Zod (or don't validate at all), then separately type your handler. Elysia unifies validation and typing into one declaration. Define it once, get runtime validation and compile-time types together.

Runtime matters. Elysia runs on Bun. Next.js API Routes run on Node.js (or Vercel's serverless). Bun is faster for most workloads, but it's newer and has a smaller ecosystem. If you need a specific Node.js package that hasn't been tested on Bun, that could be an issue.

Framework independence. Next.js API Routes exist inside Next.js. Elysia is standalone. You can pair Elysia with any frontend, deploy it anywhere Bun runs, and evolve it independently. That decoupling is valuable if your architecture changes.

Plugin ecosystem. Elysia has a growing plugin system for common needs: JWT auth, CORS, Swagger docs, GraphQL, WebSockets. It's not as mature as Express middleware, but the essentials are covered and the plugin API is clean.

Deployment options. API Routes deploy to Vercel with zero config. Elysia needs a Bun-compatible host. You can use a VPS, Docker, or Fly.io. It's slightly more setup, but you get more control over your runtime environment.

When to Choose Next.js API Routes

• You're already building a Next.js frontend and the API is simple
• You want Vercel's zero-config deployment
• The backend is fewer than 10-15 endpoints
• You don't want to manage a separate server process
• The API is tightly coupled to your frontend

When to Choose Elysia

• You want end-to-end type safety with zero boilerplate
• Performance matters and you're interested in Bun
• You're building a standalone API that serves multiple clients
• You appreciate modern DX with auto-generated Swagger docs
• You want a dedicated backend framework that stays lightweight

The Verdict

Elysia is one of the most exciting backend frameworks I've worked with recently. The type safety story is better than anything else in the JavaScript ecosystem. If you're starting a new API project and you're open to running Bun instead of Node, Elysia is worth serious consideration.

Next.js API Routes win on convenience when you're already in the Next.js ecosystem. But for building a real backend that goes beyond basic endpoints, Elysia offers a better developer experience with stronger typing, better performance, and actual framework structure.

For solo developers specifically, Elysia's type inference eliminates an entire category of bugs without adding boilerplate. That trade-off, slightly newer ecosystem for significantly better DX, is one I'd take for most new projects.