Full Stack Developer (Python/React)

This role is best suited for a Middle to Senior Full Stack Developer with strong experience in Python and React, who enjoys building modern web applications in a remote, client-focused environment. The candidate should be proficient in Python (Django, Flask, or FastAPI), React, JavaScript/TypeScript, HTML, CSS, REST APIs, PostgreSQL/MySQL, Git, SQL, and web development best practices, with Docker, CI/CD, cloud deployments, and ETL experience as valuable additions. They should be familiar with developing full-stack web applications, designing APIs, working with relational databases, collaborating with cross-functional teams, translating client requirements into software solutions, and maintaining clean, production-quality code.

1. How would you design a RESTful API using FastAPI for a data-intensive application?
   Answer: I would organize the application into routers, services, and repositories, use Pydantic models for validation, implement dependency injection, proper exception handling, pagination, authentication, and automatic OpenAPI documentation.

2. What are the main differences between Django, Flask, and FastAPI, and when would you choose each?
   Answer: Django is a full-featured framework with batteries included, Flask is lightweight and flexible, while FastAPI is optimized for high-performance APIs with async support and automatic type validation. The choice depends on project complexity and performance requirements.

3. How do you optimize database performance when working with PostgreSQL and SQLAlchemy?
   Answer: I optimize queries by using indexes, eager loading to avoid N+1 problems, connection pooling, efficient joins, and analyzing execution plans with EXPLAIN ANALYZE.

4. How would you structure a React + TypeScript application for long-term maintainability?
   Answer: I organize the project by feature modules, separate UI from business logic, create reusable components and custom hooks, use strict TypeScript typing, and maintain consistent code quality with linting and testing.

5. Explain how asynchronous programming works in Python and when you would use it.
   Answer: Python's async/await allows non-blocking execution for I/O-bound operations such as API calls or database requests. It improves throughput and resource utilization without creating additional threads for every request.

6. How do you ensure the quality of your code before deployment?
   Answer: I write unit and integration tests, perform code reviews, use static analysis and formatting tools, run automated CI pipelines, and verify functionality in staging before production deployment.

7. Describe your experience working with Docker in a development workflow.
   Answer: I use Docker to create reproducible environments, containerize backend and frontend services, manage dependencies consistently across machines, and simplify deployment through Docker Compose or orchestration platforms.

8. What SOLID principles do you apply most often in your Python projects?
   Answer: I frequently apply the Single Responsibility Principle to keep classes focused, Dependency Inversion for easier testing and extensibility, and Open/Closed Principle to extend functionality without modifying existing code.

9. How would you design an ETL pipeline for processing pharmaceutical or scientific data?
   Answer: I would separate extraction, transformation, and loading stages, validate data quality, implement logging and retry mechanisms, process data incrementally where possible, and monitor pipeline execution for failures and performance.

10. Describe a challenging full-stack project where you collaborated directly with clients or stakeholders.
    Answer: I gathered requirements through regular discussions, translated business needs into technical solutions, delivered backend APIs and frontend features iteratively, incorporated user feedback, and ensured the final product met both technical and business goals.

Appsilon is a fully remote, open-source consultancy building modern web applications that help global pharmaceutical and life sciences companies accelerate research and make better data-driven decisions. As a Full Stack Developer, you'll develop production-grade applications using Python (Django, Flask, or FastAPI), React, TypeScript, REST APIs, and PostgreSQL/MySQL, while collaborating with experienced engineers in a remote-first environment. This full-time role is open across Europe and LATAM, offering PLN 15,000–18,900/month (B2B), flexible working hours, professional development support, and a transparent career growth framework. If you enjoy solving meaningful technical challenges with modern technologies while contributing to impactful healthcare innovation, Appsilon is an excellent place to grow your career.