Agent-Skills.md

Agent Skills: Event Store Design

Design and implement event stores for event-sourced systems. Use when building event sourcing infrastructure, choosing event store technologies, or implementing event persistence patterns.

UncategorizedID: wshobson/agents/event-store-design

Repository

wshobson/agents
wshobsonLicense: MIT
32,1353,507

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pnpm dlx add-skill https://github.com/wshobson/agents/tree/HEAD/plugins/backend-development/skills/event-store-design

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plugins/backend-development/skills/event-store-design/SKILL.md

Skill Metadata

Name
event-store-design
Description
Design and implement event stores for event-sourced systems. Use when building event sourcing infrastructure, choosing event store technologies, or implementing event persistence patterns.

Event Store Design

Comprehensive guide to designing event stores for event-sourced applications.

When to Use This Skill

  • Designing event sourcing infrastructure
  • Choosing between event store technologies
  • Implementing custom event stores
  • Optimizing event storage and retrieval
  • Setting up event store schemas
  • Planning for event store scaling

Core Concepts

1. Event Store Architecture

┌─────────────────────────────────────────────────────┐
│                    Event Store                       │
├─────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐ │
│  │   Stream 1   │  │   Stream 2   │  │   Stream 3   │ │
│  │ (Aggregate)  │  │ (Aggregate)  │  │ (Aggregate)  │ │
│  ├─────────────┤  ├─────────────┤  ├─────────────┤ │
│  │ Event 1     │  │ Event 1     │  │ Event 1     │ │
│  │ Event 2     │  │ Event 2     │  │ Event 2     │ │
│  │ Event 3     │  │ ...         │  │ Event 3     │ │
│  │ ...         │  │             │  │ Event 4     │ │
│  └─────────────┘  └─────────────┘  └─────────────┘ │
├─────────────────────────────────────────────────────┤
│  Global Position: 1 → 2 → 3 → 4 → 5 → 6 → ...     │
└─────────────────────────────────────────────────────┘

2. Event Store Requirements

| Requirement | Description | | ----------------- | ---------------------------------- | | Append-only | Events are immutable, only appends | | Ordered | Per-stream and global ordering | | Versioned | Optimistic concurrency control | | Subscriptions | Real-time event notifications | | Idempotent | Handle duplicate writes safely |

Technology Comparison

| Technology | Best For | Limitations | | ---------------- | ------------------------- | -------------------------------- | | EventStoreDB | Pure event sourcing | Single-purpose | | PostgreSQL | Existing Postgres stack | Manual implementation | | Kafka | High-throughput streaming | Not ideal for per-stream queries | | DynamoDB | Serverless, AWS-native | Query limitations | | Marten | .NET ecosystems | .NET specific |

Templates and detailed worked examples

Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.

Best Practices

Do's

  • Use stream IDs that include aggregate type - Order-{uuid}
  • Include correlation/causation IDs - For tracing
  • Version events from day one - Plan for schema evolution
  • Implement idempotency - Use event IDs for deduplication
  • Index appropriately - For your query patterns

Don'ts

  • Don't update or delete events - They're immutable facts
  • Don't store large payloads - Keep events small
  • Don't skip optimistic concurrency - Prevents data corruption
  • Don't ignore backpressure - Handle slow consumers