System Design Interview

Database Sharding

Learn how to partition your database for massive scale. Explore different sharding keys, the challenges of rebalancing, and how to handle cross-shard transactions.

Example: Hash-Based Sharding Logic in Python

A simple function to determine which shard a given key belongs to using a hash-based approach. This is a common way to distribute data evenly.


                                class HashSharding:
                                    def __init__(self, num_shards):
                                        self.num_shards = num_shards
                                
                                    def get_shard(self, key):
                                        # Use a simple hash function (in a real system, a more robust hash like MD5 or SHA-1 would be used)
                                        hashed_key = hash(key)
                                        shard_id = hashed_key % self.num_shards
                                        return shard_id

Our AI Coach can help you explore the pros and cons of different sharding keys and discuss complex topics like consistent hashing to minimize data movement when re-sharding.