They are only using leading technologies combined with well designed architectures.
1. Mobile Android, iOS: Android SDK, Objective C, Swift, Java, XML.
2. Frontend: Front-End HTML5, CSS/CSS 3, JavaScript.
3. Backend: Java EE/Java SE, PHP, GoLang, Ruby, Python.
4. Databases: Mysql, Oracle, PostgreSQL, MS SQL, SQLite, MongoDb.
5. Testing: Manual & Automation testing.
6. Frameworks: Angular Js, React JS, Symfony2, Laravel, Silex, Spring MVC, Rails, Django, Pyramid, Protractor, Sellenium.
7. UI/UX: Photoshop, Sketch, Zeplin, Invision, Moqups.
8. Server Administration: Amazon Web Services, Digital Ocean, LAMP, Cloud, Apache, Apache Tomcat, NGINX.