What is the difference between sharding and replication?

Question

Accepted Answer

**Sharding** — splitting data horizontally. **Replication** — copying data.

**Sharding:**
- Split data across servers.
- Each shard has different data.
- Horizontal scaling.
- Complex queries across shards.

```
Sharding:
Shard 1: Users A-M
Shard 2: Users N-Z
(Each shard has different data)
```

**Replication:**
- Copy data to multiple servers.
- Each replica has same data.
- High availability.
- Read scaling.

```
Replication:
Primary → Replica 1 (copy)
       → Replica 2 (copy)
(All have same data)
```

**Key differences:**
- **Sharding** — different data per server.
- **Replication** — same data per server.
- **Sharding** — write scaling.
- **Replication** — read scaling.

Systems Analyst: What is the difference between sharding and replication?