Why write your alert in query language?

Builder mode lets you build a query by picking metrics and filters from menus. Code mode lets you type PromQL yourself, which is often clearer for multi-step math like ratios.

In this path, you use Code mode to alert on QuickPizza’s error rate: the percentage of requests that fail. That query divides failed requests by all requests, then scales the result to a percentage. You can write that pattern directly in Code mode.

When to reach for Code mode

Code mode is worth it when your alert needs:

• A percentage or ratio. For example, failed requests as a share of all requests, written as one PromQL expression.
• Custom or multi-step math. Patterns that are awkward to assemble from menus alone.
• To compare two metrics. For example, current usage against a capacity limit on a different series.
• A query you already trust. Paste one in from a dashboard or a teammate.

What you’ll build

Step by step, you build every part of the rule:

• The PromQL query that measures error rate
• The threshold that decides when to fire
• A folder and labels so the alert is easy to find and organize
• How often Grafana checks the rule, and how long the problem must last before firing
• Rules for handling missing data
• The contact point and message that tell someone what’s wrong

You’ll use QuickPizza, a demo pizza shop you install in Grafana Cloud. The next milestone walks through that install.