The best choice among Express.js, Django, or Next.js API for your blog app depends on your specific requirements, preferences, and prior experience. Here’s a breakdown to help you decide:

1. Express.js Strengths: Lightweight and fast. Highly flexible; allows you to design the architecture as you like. Rich ecosystem of npm packages. Full control over how routes and middleware are set up. Suitable for both RESTful and GraphQL APIs. Best for: Developers familiar with JavaScript/Node.js. Scenarios where you need maximum control and customization. Lightweight APIs or microservices. Challenges: Requires more boilerplate compared to Django and Next.js API. You’ll need to set up features like authentication, ORM (e.g., Sequelize, Prisma), and validation manually.

2. Django Strengths: Python-based framework with a "batteries included" philosophy. Comes with built-in admin interface, ORM (Django ORM), and authentication system. Highly secure and scalable. Suitable for rapid development of robust and reliable APIs. Great for APIs that involve complex relational data, thanks to Django REST Framework (DRF). Best for: Python developers or those comfortable with Python. Projects needing fast implementation and rich built-in functionality. When you prefer to focus more on business logic than boilerplate code. Challenges: Slightly heavier than Express.js or Next.js API. Less flexibility compared to Express.js (although Django can be extended).

3. Next.js API Strengths: Built-in API routes integrated into the framework. Perfect for applications that combine frontend and backend in one codebase. Optimized for serverless deployment (e.g., Vercel). Easy to use if your app already uses Next.js for the frontend. API routes automatically scale in serverless environments. Best for: Developers familiar with React and Next.js. Apps where frontend and backend logic are tightly coupled. Serverless-first projects or those needing minimal backend complexity. Challenges: Not as feature-complete for complex APIs as Django or standalone Express.js. Might not be ideal for a standalone backend, as it is more suited for apps combining frontend and backend.

Recommendation: Go with Express.js if you: Want maximum control and flexibility. Are experienced with JavaScript and prefer a lightweight API solution. Go with Django if you: Want an all-in-one solution with minimal boilerplate. Are building a complex blog that involves relational data or needs high security. Go with Next.js API if you: Already use Next.js for your frontend. Prefer an integrated solution with a serverless-first approach. Since you already have Django experience and are learning Next.js, you might find it efficient to build the backend with Django (for rich API features) while integrating it with Next.js for the frontend. Alternatively, using Next.js API routes can simplify your stack if the backend logic isn't too complex.