Einherjar

For those who come after.

A Go framework built from battle-tested production code — organized for teams, documented for the developer who was never in the room.

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The Name

In Norse mythology, the Einherjar are the chosen — warriors who fell in battle and were carried to Valhalla by the Valkyries. There they train, day after day, preparing for Ragnarök. Not for themselves. For what comes after.

This framework carries that name deliberately. Every interface defined here, every architectural decision recorded, every module boundary enforced exists for the developer who will build on this code without ever speaking to its authors. No tribal knowledge. No implicit conventions. The documentation is the system.

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What Is This

Einherjar is a collection of composable Go modules, each addressing one infrastructure concern. The mental model is Spring Boot starters — not one framework binary, but a curated set of independent modules with isolated dependency graphs.

Each module is its own go.mod. Import only what your service needs. A minimal CRUD API requires exactly three: core + web + one db-*.

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Modules

Module	Purpose	Depends on
contracts	Pure interfaces. The constitution of the framework.	—
core	Lifecycle, logging, errors, validation	contracts
web	HTTP server, middleware, routing, health	contracts core
auth	Auth middleware, RBAC	contracts web core
auth-jwt	JWT signing, token pairs, refresh	contracts auth core
auth-firebase	Firebase authentication	contracts auth core
db-postgres	PostgreSQL client	contracts core
db-mysql	MySQL client	contracts core
db-sqlite	SQLite client	contracts core
cache-valkey	Valkey / Redis-compatible cache	contracts core
storage-minio	Object storage	contracts core
telemetry	OpenTelemetry — main packages only	contracts core
worker	Concurrent background worker pool	contracts core
httpclient	Resilient outbound HTTP client	contracts core

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Dependency Graph

contracts
└── core
     ├── web
     │    └── auth
     │         ├── auth-jwt
     │         └── auth-firebase
     ├── db-postgres
     ├── db-mysql
     ├── db-sqlite
     ├── cache-valkey
     ├── storage-minio
     ├── telemetry          ← import from main only
     ├── worker
     └── httpclient

Data modules (db-*, cache-*, storage-*) never import web. Repositories do not know HTTP exists. This boundary is absolute.

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The Law

contracts is the constitution of this framework — pure interfaces, zero dependencies, permanent signatures. Changes flow outward from contracts, never inward. Before any change to contracts, the blast radius is calculated: which interfaces are affected, which modules implement them, which modules consume those. Release sequence: contracts first, then implementors, then consumers.

Adding a method to a published interface is a breaking change in Go. It is not permitted without a major version bump and coordinated updates across all implementing modules.

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For Those Who Come After

Good code is not written for the machine. It is not even written for the deadline. It is written for the person who will read it at 11pm six months from now, under pressure, trying to understand what this thing does and why it was built this way.

Every ADR in this organization exists because a decision was made and the reasoning behind it matters as much as the outcome. Every interface in contracts is as small as it can be because the developer implementing it in a new context deserves to know exactly what is required and nothing more.

This is the standard. Not the deadline.

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