Source Selection

This guide helps you choose the right configuration sources for your application.

Decision Guide

Local vs Remote

Scenario	Recommended Source
Single application	Local files (JSON, YAML)
Microservices	Remote (Consul, Nacos)
Secrets management	Vault
Container deployment	Environment variables + Remote

File Format Selection

Format	Best For
JSON	Most applications, good tooling support
YAML	Complex hierarchies, human-readable
TOML	Simple configs, Rust ecosystem
INI	Legacy systems, simple key-value
XML	Enterprise systems, schema validation

Common Patterns

Development Environment

var cfg = new CfgBuilder()
    .AddJsonFile("config.json", level: 0, writeable: false)
    .AddJsonFile("config.Development.json", level: 1, writeable: false, optional: true)
    .AddJsonFile("config.local.json", level: 2, writeable: true, optional: true)
    .Build();

Production with Remote Config

var cfg = new CfgBuilder()
    .AddJsonFile("config.json", level: 0, writeable: false)
    .AddConsul(options =>
    {
        options.Address = "http://consul:8500";
        options.KeyPrefix = "myapp/config/";
    }, level: 10, writeable: true, reloadOnChange: true)
    .AddVault(options =>
    {
        options.Address = "http://vault:8200";
        options.SecretPath = "secret/myapp";
    }, level: 15, writeable: false)
    .AddEnvironmentVariables(level: 20, prefix: "MYAPP_")
    .Build();

Kubernetes Deployment

var cfg = new CfgBuilder()
    .AddJsonFile("/app/config/config.json", level: 0, writeable: false)
    .AddJsonFile("/app/secrets/secrets.json", level: 5, writeable: false, optional: true)
    .AddEnvironmentVariables(level: 10, prefix: "APP_")
    .Build();

Level Guidelines

Level Range	Purpose	Examples
0-9	Base configuration	config.json, config.yaml
10-19	Remote configuration	Consul, Nacos, Etcd
15-19	Secrets	Vault
20+	Overrides	Environment variables

Next Steps

• Config Merge - How merging works
• Config Sources - All available sources