Sharding Calculator

Estimate how many shards you need from storage ceilings and per-shard QPS, then apply growth and replica factor.

Sharding Calculator

Choose shard count from storage size and QPS capacity, then see per-shard load after growth.

Current dataset size GB Target max size / shard GB Peak QPS (cluster) Safe QPS / shard Expected growth factor e.g. 2 = double Replica factor / shard primary+replicas

Assumes relatively even key distribution. Hot keys, fan-out queries, and cross-shard transactions can invalidate perfect splits — design shard keys carefully.

Storage vs QPS Bound

Take the larger of:

shards_storage = future_data_size ÷ target_max_size_per_shard
shards_qps = future_peak_qps ÷ safe_qps_per_shard

If storage wins, you are disk/index bound. If QPS wins, you are CPU/connection/latency bound.

Shard Key Reality Check

Perfect math still fails with:

Hot keys / celebrity users
Scatter-gather queries across shards
Cross-shard transactions

Pick a shard key with high cardinality and even access patterns. Plan resharding early — moving data later is the expensive part.