# Alerting
Alerting thresholds to use for monitoring.
After setting up a monitoring tool, it is important to configure alert rules. Alert rules send a notification when a metric surpasses a threshold. This will help you prevent operational incidents.

This page describes which metrics and thresholds to build as a starting point. For more details on how to set up alert rules in Datadog or Grafana, refer to:

 * [Datadog monitors](https://docs.datadoghq.com/monitors/)
 * [Grafana alerts](https://grafana.com/docs/grafana/latest/alerting/fundamentals/)

## Thresholds

Alert rules tend to have two threshold levels, and we are going to define them as follows:
 * **Warning:** represents a call to attention to a symptom with high chances to develop into an issue.
 * **Alert:** represents an active issue that requires immediate action.

For each threshold level, use the following table as a guide to set up your own alert rules:

Metric | Warning | Alert | Description
-- | -- | -- | --
CPU | 85% | 100% | Average CPU usage for a cluster in the last *15 minutes*.
Memory | 80% | 90% | Average memory usage for a cluster in the last *15 minutes*.
Source status | - | On Change | Source status change in the last *1 minute*.
Cluster status | - | On Change | Cluster replica status change in the last *1 minute*.
Freshness | > 5s | > 1m | Average [lag behind an input](/reference/system-catalog/mz_internal/#mz_materialization_lag) in the last *15 minutes*.

### Custom Thresholds

For the following table, replace the two variables, _X_ and _Y_, by your organization and use case:

Metric | Warning | Alert | Description
-- | -- | -- | --
Latency | Avg > X | Avg > Y | Average latency in the last *15 minutes*. Where X and Y are the expected latencies in milliseconds.
Credits | Consumption rate increase by X% | Consumption rate increase by Y% | Average credit consumption in the last *60 minutes*.