⚙️ Backend Engineering · Distributed Systems

Adopt event sourcing without the graveyard mistakes

Command/event separation, upcasting discipline, and projection rebuild strategies that survive year three.

advanced~45 minBackend EngineersAPI DevelopersPlatform Engineers

Steps

1Store commands' resulting EVENTS as truth; never store mutable state alongside
2Version events immutably; upcast old versions at read boundaries only
3Build projections as disposable rebuilds from the stream — test rebuilds regularly
4Snapshot aggressively enough that replays don't take hours
5Keep event payloads primitively typed; rich behavior belongs in handlers
6Answer 'why did state change' queries from streams — that's the payoff

Common Pitfalls

▲Events named after tables (UserUpdated) carrying no business meaning
▲Schema changes editing history instead of adding versions

Commands

Install with skills CLI

$ npx skills add aniruddhaadak80/skills --skill distributed-systems-event-sourcing-pragmatics

Install globally

$ npx skills add aniruddhaadak80/skills --skill distributed-systems-event-sourcing-pragmatics -g

Tags

#event-sourcing#architecture#cqrs#backend-engineering#distributed-systems

Install this skill

$ npx skills add aniruddhaadak80/skills --skill distributed-systems-event-sourcing-pragmatics -a opencode

SKILL.md

# Adopt event sourcing without the graveyard mistakes

> Command/event separation, upcasting discipline, and projection rebuild strategies that survive year three.

## When to Use This Skill

Command/event separation, upcasting discipline, and projection rebuild strategies that survive year three.

## Steps

1. Store commands' resulting EVENTS as truth; never store mutable state alongside
2. Version events immutably; upcast old versions at read boundaries only
3. Build projections as disposable rebuilds from the stream — test rebuilds regularly
4. Snapshot aggressively enough that replays don't take hours
5. Keep event payloads primitively typed; rich behavior belongs in handlers
6. Answer 'why did state change' queries from streams — that's the payoff

## Common Pitfalls

- Events named after tables (UserUpdated) carrying no business meaning
- Schema changes editing history instead of adding versions

View source on GitHub ↗

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