# Big tenant hot shard

> The biggest tenant's key landed on one shard. Its reads and writes cost 3× the CPU, and everything else on that shard waits behind it.

## What happens

The biggest tenant's key landed on one shard. Its reads and writes cost 3× the CPU, and everything else on that shard waits behind it.

## How to prevent it

Shard the tenant by key, and keep its reads in a Cache in front of the Database.

The postmortem opens the first of these that you do not own yet:

- [Sharding](https://wiki.playquorum.dev/research/sharding.md)
- [Caching](https://wiki.playquorum.dev/research/caching.md)

## Components it hits

[Database](https://wiki.playquorum.dev/components/database.md)

## Facts

SEV2 Big tenant hot shard
- **First Era:** [Series B](https://wiki.playquorum.dev/eras/series-b.md)
- **Starts at:** SEV2
- **Escalates to:** SEV1
- **Lasts:** 1.5 min

## See also

- [Incidents](https://wiki.playquorum.dev/incidents.md)

Source: https://wiki.playquorum.dev/incidents/hot-shard