Short answer
In business systems and web development, JavaScript and TypeScript, Python, PHP, Java, C# and Go are widespread. More important for the client than the specific language is whether the technology is widespread and maintainable, whether it has a mature framework and whether you’ll be able to find developers to keep developing the system.
The most widespread languages and their uses
- JavaScript / TypeScript — web interfaces, and servers too (Node.js).
- Python — data processing, machine learning, AI agents, automation.
- PHP — web systems and platforms (Laravel, Symfony, Yii).
- Java and C# — large enterprise systems.
- Go — fast services and infrastructure.
- Kotlin and Swift — mobile apps.
What the client should check
- Popularity — will it be easy to find developers in the future?
- Framework — is a mature, supported framework used rather than something “home-made”?
- Documentation and tests — will another developer be able to continue the work?
- Source code — who owns it? See who owns the source code of a custom system.
What we use
For web systems — PHP with the Symfony, Laravel and Yii 2.0 frameworks; for interfaces — Vue.js and TypeScript; for AI and data processing — Python; for databases — PostgreSQL and MySQL; plus Docker and cloud infrastructure. The choice always depends on the project.