When should you actually start sharding?
Sharding is powerful but hard to reverse. Designing a shard key, rewriting application logic, and shrinking transaction scope are all expensive, so the balance between "preparing too early" and "adopting too late" matters. This tool calculates your current storage and QPS usage ratios to help you estimate when sharding actually becomes necessary.
As a rule of thumb, once you cross 80% of your server's recommended capacity or throughput, performance degradation and outage risk rise sharply. In the 50-80% range you still have time, but factoring in your monthly growth rate to plan your shard key and migration strategy early is the safer move. Below 50%, low-cost fixes like index optimization, query tuning, and read replicas are usually enough.
Once you decide to shard, pick a shard key that fits your service (user ID, region, time-based, etc.) first, and design for gradual migration — dual writes and a proxy layer make the transition far less risky.
Frequently Asked Questions
Before sharding, try index optimization, read replicas, caching, or scaling up the server first — these are usually far more cost-effective.
You don't need to adopt it now, but designing your shard key early can drastically cut migration costs later.
It depends on your service. Read/write-heavy services usually hit QPS limits first, while data-accumulating services hit storage limits first.