What Elixir Developers Actually Build
Elixir is used for building high-concurrency, real-time, and distributed systems. Here's where Elixir developers work:
Real-Time Applications
Elixir/Phoenix excels at real-time features:
- Chat applications - Discord, Slack-like real-time messaging
- Live dashboards - Real-time data updates, live analytics
- Collaborative tools - Multi-user editing, live collaboration
- Gaming backends - Real-time game state synchronization
Companies: Discord (real-time messaging), Pinterest (notification system)
High-Concurrency Systems
Elixir's concurrency model handles millions of connections:
- WebSocket servers - Thousands of concurrent connections
- API backends - High-throughput APIs
- Message queues - Background job processing
- IoT backends - Handling millions of device connections
Distributed Systems
Elixir's distributed capabilities enable:
- Microservices - Distributed service architecture
- Distributed databases - Riak, distributed data stores
- Cluster management - Distributed application coordination
Why Elixir is Powerful
Concurrency Model
Elixir runs on BEAM, enabling incredible concurrency:
- Lightweight processes - Millions of processes can run simultaneously
- Actor model - Processes communicate via message passing
- No shared state - Eliminates race conditions
- Fault isolation - Process crashes don't affect others
Fault Tolerance
Elixir applications are fault-tolerant by design:
- "Let it crash" - Isolated failures are acceptable
- Supervisors - Automatic process restart
- Self-healing - Systems recover from failures automatically
Functional Programming
Elixir is functional:
- Immutability - Data structures are immutable
- Pattern matching - Powerful data destructuring
- Pipe operator - Elegant data transformation
- No side effects - Easier to reason about code
Phoenix Framework
Phoenix brings Rails-like productivity to Elixir:
- Channels - Real-time WebSocket support
- LiveView - Server-rendered reactive UI
- Ecto - Database abstraction (like ActiveRecord)
- Performance - Handles millions of connections
The Modern Elixir Developer Profile
Functional Programming Understanding
Elixir is functional. Strong candidates understand:
- Immutability - Why data structures don't change
- Pattern matching - Destructuring and matching data
- Higher-order functions - map, filter, reduce, Enum functions
- Recursion - Functional approach to iteration
Red flag: A developer who tries to write Elixir like object-oriented code won't leverage Elixir's strengths.
Concurrency & Processes
Elixir's power comes from concurrency. Strong candidates understand:
- Processes - Lightweight, isolated units of execution
- Message passing - How processes communicate
- Supervisors - Process monitoring and restart
- GenServer - Generic server behavior pattern
Phoenix Framework
Phoenix is Elixir's web framework. Strong candidates understand:
- Channels - Real-time WebSocket communication
- LiveView - Server-rendered reactive UI
- Ecto - Database abstraction and querying
- Plug - Middleware system
Common Hiring Mistakes
1. Treating Elixir Like Object-Oriented Languages
Elixir is functional and concurrent. Don't ask about classes, inheritance, or mutable state. Elixir developers think in processes, messages, and immutability.
Fix: Focus on functional programming concepts, concurrency patterns, and Phoenix framework.
2. Ignoring Functional Programming Experience
Elixir requires functional thinking. A developer who only knows OOP will struggle.
Fix: Ask about functional programming experience. "Have you worked with functional languages? Explain immutability."
3. Overemphasizing Elixir Experience
Elixir is niche. Requiring "3+ years Elixir experience" eliminates excellent candidates. Strong developers learn Elixir in 2-3 months.
Fix: Focus on functional programming understanding, concurrency concepts, and learning ability.
4. Missing Concurrency Understanding
Elixir's main advantage is concurrency. A developer who doesn't understand processes and message passing won't leverage Elixir.
Fix: Ask about concurrency. "Explain the actor model. How do processes communicate in Elixir?"
Recruiter's Cheat Sheet
Resume Green Flags
- Functional programming experience (Haskell, F#, Clojure, Scala)
- Concurrency experience (Erlang, Go, concurrent systems)
- Phoenix/LiveView experience
- Real-time application experience
- Distributed systems experience
- Open source Elixir contributions
Resume Yellow Flags
- Only object-oriented experience
- No functional programming background
- Generic "backend developer" without specifics
- No concurrency understanding
- No real-time application experience
Technical Terms to Know
| Term | What It Means |
|---|---|
| BEAM | Erlang Virtual Machine (runs Elixir) |
| Process | Lightweight unit of concurrency (not OS process) |
| Actor Model | Concurrency model (processes communicate via messages) |
| GenServer | Generic server behavior pattern |
| Supervisor | Process that monitors and restarts other processes |
| Phoenix | Elixir's web framework |
| LiveView | Server-rendered reactive UI |
| Ecto | Database abstraction library |
| Pattern Matching | Destructuring and matching data structures |
| Pipe Operator |
Questions That Reveal Skill Level
| Question | Junior Answer | Senior Answer |
|---|---|---|
| "Explain Elixir's concurrency model" | "It has processes" | Explains BEAM, lightweight processes, message passing, actor model, supervisors |
| "How do you handle state in Elixir?" | "You don't" | Explains GenServer, Agent, ETS, when to use each, immutability benefits |
| "What's the difference between Elixir and Erlang?" | "Elixir is newer" | Explains syntax differences, tooling, ecosystem, same BEAM VM |
Skills Assessment by Use Case
If You're Building Real-Time Applications
- Priority: Phoenix Channels, LiveView, WebSocket handling, concurrency
- Interview focus: "Design a real-time chat system with Elixir"
- Red flag: No understanding of WebSockets or concurrency
If You're Building High-Concurrency APIs
- Priority: Process management, message passing, fault tolerance
- Interview focus: "How would you handle 1 million concurrent connections?"
- Red flag: No understanding of concurrency or processes
If You're Building Distributed Systems
- Priority: Distributed Erlang, cluster management, fault tolerance
- Interview focus: "How would you build a distributed system with Elixir?"
- Red flag: No understanding of distributed systems