---
name: database-sharding
description: >
  Implement database sharding for horizontal scalability. Use when scaling large
  databases, distributing data across multiple servers, or designing sharded
  architectures.
---

# Database Sharding

## Table of Contents

- [Overview](#overview)
- [When to Use](#when-to-use)
- [Quick Start](#quick-start)
- [Reference Guides](#reference-guides)
- [Best Practices](#best-practices)

## Overview

Implement horizontal data partitioning across multiple database servers. Covers sharding strategies, consistent hashing, shard key selection, and cross-shard querying patterns.

## When to Use

- Database size exceeds single server capacity
- Read/write throughput needs horizontal scaling
- Geographic data distribution requirements
- Multi-tenant data isolation
- Cost optimization through distributed architecture
- Load balancing across database instances

## Quick Start

Minimal working example:

```sql
-- Define shard ranges
-- Shard 0: user_id 0-999999
-- Shard 1: user_id 1000000-1999999
-- Shard 2: user_id 2000000-2999999

CREATE TABLE users_shard_0 (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id BIGINT NOT NULL,
  email VARCHAR(255) NOT NULL,
  created_at TIMESTAMP DEFAULT NOW(),
  CONSTRAINT shard_0_range CHECK (user_id BETWEEN 0 AND 999999)
);

CREATE TABLE users_shard_1 (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id BIGINT NOT NULL,
  email VARCHAR(255) NOT NULL,
  created_at TIMESTAMP DEFAULT NOW(),
  CONSTRAINT shard_1_range CHECK (user_id BETWEEN 1000000 AND 1999999)
);

-- Function to determine shard
CREATE OR REPLACE FUNCTION get_shard_id(p_user_id BIGINT)
RETURNS INT AS $$
BEGIN
// ... (see reference guides for full implementation)
```

## Reference Guides

Detailed implementations in the `references/` directory:

| Guide | Contents |
|---|---|
| [Range-Based Sharding](references/range-based-sharding.md) | Range-Based Sharding |
| [Hash-Based Sharding](references/hash-based-sharding.md) | Hash-Based Sharding |
| [Directory-Based Sharding](references/directory-based-sharding.md) | Directory-Based Sharding |

## Best Practices

### ✅ DO

- Follow established patterns and conventions
- Write clean, maintainable code
- Add appropriate documentation
- Test thoroughly before deploying

### ❌ DON'T

- Skip testing or validation
- Ignore error handling
- Hard-code configuration values


---
Source attribution: aj-geddes
Original project: https://github.com/aj-geddes/useful-ai-prompts/blob/3f5182cfd739fc113f4af5244a1cf342ad7f7911/skills/database-sharding/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Copyright (c) 2025 AJ Geddes

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.


# Dave AI resource metadata

Creator / publisher: aj-geddes
Original project: https://github.com/aj-geddes/useful-ai-prompts/blob/3f5182cfd739fc113f4af5244a1cf342ad7f7911/skills/database-sharding/SKILL.md
Attribution basis: Recovered original package and original project license at a pinned revision

Fields of work: Development & Engineering
Roles: Backend Developer, Data Engineer, Database Administrator
Specialties: Database
Tools: PostgreSQL
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: c3afd207227f43ade77cbdf0d4a78810381e3d16dc1af08e80852f3797df1770
Metadata reviewed: 2026-10-27
This metadata supersedes earlier Dave AI catalog attribution. Original instruction and supporting files are preserved.