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In the Field
Overview

Overview

Ready to build production Elixir systems? This In-the-Field guide teaches production patterns by following the OTP-First principle, ensuring you understand BEAM foundations before frameworks.

What Is “In the Field”?

In-the-Field guides teach production Elixir development through real-world implementation patterns. Unlike by-example tutorials that achieve 95% language coverage, these guides focus on specific production scenarios using industry-standard frameworks, libraries, and enterprise patterns.

Key distinction: By-example taught Elixir through code. In-the-field teaches how to build production systems with Elixir.

These guides address framework adoption decisions: When do I need Phoenix? When is Ecto appropriate? Should I use raw GenServer or a higher-level abstraction? Each guide shows the progression from OTP primitives to production frameworks.

OTP-First Philosophy

Elixir’s true power lies in OTP (Open Telecom Platform), the battle-tested framework built into the BEAM VM. Unlike other languages where frameworks are mandatory, Elixir provides production-ready concurrency and fault-tolerance tools built-in:

  • Processes and message passing - Lightweight concurrency primitives
  • GenServer - Generic server abstraction for state management
  • Supervisor trees - Automatic fault recovery and process supervision
  • Application behavior - Application lifecycle management
  • Process registries - Named process lookup and discovery

Our Approach: Learn OTP primitives first, understand when they’re insufficient, then adopt frameworks with full knowledge of trade-offs.

Why This Matters

  1. Foundation understanding - Know BEAM primitives before Phoenix abstractions
  2. Informed framework selection - Understand problems Phoenix and Ecto solve
  3. Problem awareness - See manual implementation complexity without frameworks
  4. Framework independence - Core OTP knowledge transfers across tools
  5. Trade-off comprehension - Recognize when frameworks add value vs overhead
  6. Debugging capability - Understand what frameworks do under the hood
  7. Optimization skills - Recognize performance bottlenecks in process design
  8. Production disaster prevention - Avoid process leaks, supervision errors, message queue overflow

Each guide follows this progression: OTP primitives → Limitations → Framework adoption

Guide Organization

The 36 guides are organized into 7 categories:

1. Foundation (2 guides)

Core best practices and anti-patterns for production Elixir:

2. OTP and Concurrency (7 guides)

Fundamental BEAM concurrency and OTP patterns:

3. Data Structures (6 guides)

Pattern matching and data structure patterns:

4. Web Development (6 guides)

Web application development with Phoenix and Ecto:

5. Testing and Quality (4 guides)

Testing strategies and code quality:

6. Production Deployment (7 guides)

Production-ready patterns for reliability and performance:

7. Build and Ecosystem (4 guides)

Build tooling and ecosystem integration:

Progressive Learning Path

Each guide follows this structure:

  1. Why It Matters - Production context and real-world scenarios
  2. OTP Primitives First - Built-in approach with annotated examples
  3. Limitations - When OTP primitives insufficient for production
  4. Production Framework - Industry-standard solutions with examples
  5. Trade-offs - Clear comparison tables (complexity, learning curve, maintenance)
  6. Best Practices - Actionable guidance with code examples

Example Progression (Web Development) 

  %% Color Palette: Blue #0173B2, Orange #DE8F05, Teal #029E73, Purple #CC78BC, Brown #CA9161
graph LR
    A["OTP Primitives<br/>GenServer + Plug"] -->|Limitations:<br/>No routing<br/>No lifecycle<br/>Manual setup| B["Production Framework<br/>Phoenix"]

    style A fill:#0173B2,stroke:#000,color:#fff
    style B fill:#029E73,stroke:#000,color:#fff

OTP Primitives: You can build web servers with GenServer + Plug, handling HTTP manually.

Limitations: No routing patterns, no request lifecycle, no asset pipeline, manual middleware chains, verbose context handling.

Production Framework: Phoenix provides routing, lifecycle hooks, LiveView, Channels, asset pipeline, and structured patterns.

Trade-off: Learn GenServer and Plug first to understand what Phoenix abstracts away.

Code Annotation Standard

All code examples maintain 1.0-2.25 annotation density (comment lines per code line) using # => notation to explain values, states, and outputs.

Example:

# OTP GenServer for state management
defmodule Counter do
  use GenServer                              # => Imports GenServer behavior
                                             # => Provides init, handle_call, etc.

  def start_link(initial \\ 0) do
    GenServer.start_link(__MODULE__, initial, name: __MODULE__)
                                             # => Starts process, registers name
                                             # => initial: Starting state
                                             # => Returns {:ok, pid}
  end

  def init(initial) do
    {:ok, initial}                           # => Initial state: initial value
                                             # => Type: {:ok, integer()}
  end

  def increment do
    GenServer.call(__MODULE__, :increment)   # => Synchronous call to registered process
                                             # => Returns new value
  end

  def handle_call(:increment, _from, state) do
    new_state = state + 1                    # => Increment state
    {:reply, new_state, new_state}           # => Reply with new value, update state
                                             # => Type: {:reply, integer(), integer()}
  end
end

Who Should Use These Guides?

  • Elixir developers building production systems - Learn industry patterns
  • Teams adopting Elixir for backend services - Establish production conventions
  • Developers transitioning from other languages - Understand Elixir production ecosystem
  • Anyone seeking production-ready Elixir patterns - Framework selection, trade-offs, best practices

Prerequisite Knowledge

These guides assume familiarity with Elixir fundamentals. If you’re new to Elixir, start with:

  • Initial Setup - 0-5% Elixir coverage (installation, tooling)
  • Quick Start - 5-30% Elixir coverage (basic syntax, first program)
  • By Example - 75-95% Elixir coverage (75+ annotated examples)

Minimum: Complete Quick Start (5-30% coverage) before starting In-the-Field guides.

Recommended: Complete By Example (75-95% coverage) for comprehensive foundation.

Learning Approach

Not a comprehensive tutorial: These guides target specific production scenarios, not sequential skill building. Jump to relevant topics based on your project needs.

Code-first learning: Examples are self-contained and runnable. Copy, execute, modify, experiment.

Framework pragmatism: We teach OTP primitives first, but recommend frameworks when they provide clear production value.

Convention Reference

These guides follow the In-the-Field Convention, which defines production implementation guide standards.

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