What Flask Developers Actually Build
Flask is used for building APIs, web applications, and microservices. Here's where Flask developers work:
REST APIs
Flask excels at building APIs:
- RESTful APIs - Simple, clean API endpoints
- Microservices - Lightweight services that communicate via HTTP
- Internal tools - Admin panels, dashboards, internal APIs
- Third-party integrations - APIs for external services
Companies: Netflix (microservices), LinkedIn (internal APIs), Pinterest (API layer), Reddit (various services)
Web Applications
Flask can build full-stack applications:
- Small to medium web apps - Blogs, portfolios, dashboards
- Prototypes - Quick MVPs and proof-of-concepts
- Custom applications - When Django is too much, Flask fits perfectly
- Hybrid apps - Mix of API endpoints and server-rendered pages
Microservices Architecture
Flask's lightweight nature makes it ideal for microservices:
- Service-oriented architecture - Individual services with Flask
- API gateways - Routing and request handling
- Background workers - Task queues and job processing
Why Flask Over Django?
Flask: Minimal & Flexible
- Micro framework - Only includes essentials
- Freedom to choose - Pick your own database, ORM, authentication
- Simple learning curve - Easy to get started
- Lightweight - Fast startup, low overhead
Django: Batteries Included
- Full-featured - Admin panel, ORM, authentication built-in
- Opinionated - Django's way or the highway
- Rapid development - More features out of the box
- Enterprise-ready - Better for large, complex applications
Reality: Many teams use Flask for APIs/microservices and Django for admin/full-stack parts. Flask is perfect when you need flexibility; Django is better when you want structure.
The Modern Flask Developer Profile
Understanding Flask's Philosophy
Flask is minimal by design. Strong candidates understand:
- Micro framework concept - What Flask includes vs. what you add
- Extension ecosystem - Flask-SQLAlchemy, Flask-Login, Flask-RESTful
- Application factory pattern - Structuring Flask apps properly
- Blueprint organization - Modular route organization
Red flag: A developer who expects Flask to work like Django won't appreciate Flask's flexibility.
Architecture Skills
Flask doesn't enforce structure. Strong candidates can:
- Design application structure - Organize routes, models, views
- Choose appropriate extensions - Know when to use Flask-SQLAlchemy vs raw SQL
- Handle configuration - Environment-based config, secrets management
- Structure for scale - Blueprints, application factories, testing patterns
Python Fundamentals
Flask is Python. Strong candidates understand:
- Python best practices - PEP 8, virtual environments, package management
- WSGI - Understanding how Flask works under the hood
- Context locals - Flask's request, session, g objects
- Decorators - Understanding Flask's route decorators
Common Hiring Mistakes
1. Treating Flask Like Django
Flask is NOT Django. Don't ask about Django ORM, admin panels, or Django-specific patterns. Flask developers work with SQLAlchemy (or raw SQL), choose their own auth, and structure apps differently.
Fix: Focus on Flask-specific patterns: Blueprints, application factories, Flask extensions.
2. Ignoring Architecture Skills
Flask doesn't enforce structure. A developer who only knows Flask tutorials will create messy codebases. Look for architectural thinking.
Fix: Ask about how they structure Flask applications. "Show me how you organize routes, models, and business logic in Flask."
3. Overemphasizing Framework Experience
Flask is relatively simple. A strong Python developer learns Flask in days. Don't require "5+ years Flask experience."
Fix: Focus on Python fundamentals and problem-solving. Flask knowledge follows naturally.
4. Missing Extension Knowledge
Flask relies on extensions. A developer who doesn't know Flask-SQLAlchemy, Flask-Login, or Flask-RESTful will struggle.
Fix: Ask about Flask extensions they've used. "What extensions do you use for database, authentication, and API building?"
Recruiter's Cheat Sheet
Resume Green Flags
- Production Flask experience with scale metrics
- Mentions of Blueprints and application factories
- Flask extension experience (SQLAlchemy, Login, RESTful)
- API design experience
- Database integration experience
- Testing experience (pytest, Flask-Testing)
Resume Yellow Flags
- Only tutorial projects (Todo apps, basic CRUD)
- No mention of Blueprints or application structure
- Generic "Python developer" without Flask specifics
- No extension experience
- No testing experience
Technical Terms to Know
| Term | What It Means |
|---|---|
| Blueprint | Flask's way to organize routes into modules |
| Application Factory | Pattern for creating Flask apps (better for testing) |
| Flask-SQLAlchemy | Extension for database integration |
| Flask-Login | Extension for user session management |
| Flask-RESTful | Extension for building REST APIs |
| WSGI | Web Server Gateway Interface (how Flask runs) |
| Jinja2 | Template engine Flask uses (but can be replaced) |
Questions That Reveal Skill Level
| Question | Junior Answer | Senior Answer |
|---|---|---|
| "Explain Flask's philosophy" | "It's a web framework" | Explains micro framework concept, flexibility, extension ecosystem |
| "How do you structure a large Flask app?" | "Put everything in app.py" | Discusses Blueprints, application factories, separation of concerns |
| "How do you handle database connections?" | "I use Flask-SQLAlchemy" | Explains connection pooling, session management, testing patterns |
Skills Assessment by Use Case
If You're Building REST APIs
- Priority: Flask-RESTful or plain Flask routes, API design, request handling
- Interview focus: "Design a REST API for [your domain]"
- Red flag: Can't design RESTful APIs or handle errors properly
If You're Building Microservices
- Priority: Lightweight architecture, service communication, error handling
- Interview focus: "How would you structure Flask services?"
- Red flag: No understanding of microservices patterns
If You're Building Full-Stack Apps
- Priority: Jinja2 templating, form handling, session management
- Interview focus: "How do you handle forms and user sessions in Flask?"
- Red flag: Only knows API development, no full-stack experience