Database

Sharding

Pros

• Increased read/write throughput
• High availability - Others remains functional if one shard is down
• Facilitates horizontal scaling
• Balanced traffic load
• Improve performance

Cons

• Requires shard key
• Higher complexity to manage

Sharding strategy

• MOD
  • Use modulo to split
  • Evenly splitted
• HASH
  • Use a hashed value to split
• RANGE
  • Specific range of rows to individual shards
  • Data with timestamp
  • But most recent shard will get more IO
• TAG
  • Matches specific values

Master & Slave

• 1 Master + many slaves
• Optimize IO without caching
• Master for write, slaves for read
• Uses Replication
• Asynchronous replication can fail at times

References:

• https://towardsdev.com/databases-a-system-design-perspective-a2ba2c2d7223
• https://levelup.gitconnected.com/database-concerns-in-large-system-design-3f84b6331ff9