The full answer
Next.js is a frequent frontend choice because it supports server-side rendering and static generation, which help performance and search visibility, while TypeScript catches many errors before code runs and makes large codebases easier to maintain.
On the backend, Node.js and NestJS suit API-driven products and real-time features, and allow TypeScript across the whole stack. Python with Django or FastAPI is a strong fit for data-heavy and AI-related services. Java and .NET are common in enterprise environments with existing investments in those ecosystems.
For mobile, Flutter and React Native let one team ship iOS and Android from a shared codebase. Native Swift and SwiftUI or Kotlin and Jetpack Compose are used when an app depends heavily on device hardware, platform-specific behaviour or demanding performance.
Many products combine several of these. A typical architecture might pair a Next.js web app and a React Native mobile app with a NestJS API and a Python service for AI features, all sharing a PostgreSQL database.
These are starting points rather than rules. The final recommendation always follows discovery.