<br />

This page describes how to analyze the heatmap in a Key Visualizer scan so you
can identify the source of a Cloud Firestore performance issue.


Before you read this page, you should be familiar with the
[overview of Key Visualizer](https://firebase.google.com/docs/firestore/key-visualizer/key-visualizer).
You may also want to:

- Learn how to [open a Key Visualizer scan](https://firebase.google.com/docs/firestore/key-visualizer/keyvis-getting-started#viewing-scan).
- See examples of common [document key patterns](https://firebase.google.com/docs/firestore/key-visualizer/keyvis-patterns) or [index key patterns](https://firebase.google.com/docs/firestore/key-visualizer/keyvis-patterns-index).

## Adjusting brightness

Key Visualizer heatmaps use dark colors to indicate normal or low values, and
bright colors to indicate high values. You can adjust the color scale to
help you see patterns in the heat map.

Keep in mind that for most metrics, Key Visualizer identifies which values are
"high" and "low" based entirely on your database's usage. For example, if you
perform 20 reads per second in a specific key range and 1 read per second in
other key ranges, Key Visualizer uses a bright color for that specific key
range. Note that bright colors do not necessarily indicate a problem.

To adjust the colors that are used for different values, use the **+ / -**
buttons on either side of the **Adjust Brightness**
*brightness_6*
icon. When you increase the brightness, you lower the range of values that each
color represents; when you lower the brightness, you increase the range of
values.

To reset the brightness to the default setting, click the
**Adjust Brightness** *brightness_6*
icon .

## Zooming in on time periods and key ranges

When you open a heatmap, it displays values for the time period included
in the scan and the range of active keys in your database. If you
notice an issue during a specific time period, or in a specific range of
keys, you can zoom in to examine the issue more closely.

There are several ways to zoom in or out:

- Scroll up or down within the heatmap.
- Click the **Rectangular Zoom** *crop* button, then click and drag to select an area to enlarge.
- Press and hold the `Shift` key, then click and drag to select an area to enlarge.
- Return to the previous area of the heatmap by pressing the `Backspace` or `Delete` key.
- Zoom out to view the entire table by clicking the **Reset Zoom** *zoom_out_map* button or pressing the `R` key.

## Drilling down by key prefix

The following section describes how to drill down using a document key scan
as an example. In case of index keys, the prefix changes to group of index keys.

On the left side of a heatmap, Key Visualizer organizes keys by the
hierarchy of your database. You can use this
to drill down into the data for specific ranges of keys.

To drill down into the heatmap's data for a group of keys that share a
common prefix:

1. Move the cursor over one of the levels in the key hierarchy that appears
   to the left of the heatmap.

   Key Visualizer highlights the area of the heatmap that shows this level of
   the hierarchy. It also shows the key prefix for all of the keys at this
   level.

   ![Example of a highlighted area in a heatmap for a group of keys](https://firebase.google.com/static/docs/firestore/images/keyvis-key-prefix-hover.png)
2. Click the level of the key hierarchy that you want to examine.

   Key Visualizer zooms in on this level of the hierarchy.

   ![Example of zooming in on a level of the key hierarchy](https://firebase.google.com/static/docs/firestore/images/keyvis-key-prefix-zoomed.png)
3. Click another level of the key hierarchy to zoom in further, or press the
   `Backspace` or `Delete` key to return to the previous area.

## Pinning details about a metric

As you move your cursor over a heatmap, Key Visualizer displays a tooltip that
contains details about the metric that is under the cursor. You can pin this
tooltip in place by clicking on the heatmap. Pinned tooltips show more detail
about the metric. Pinning a tooltip also makes it easier to take a screenshot of
the tooltip or copy information from the tooltip.

## Switching metrics

By default, when you open a Key Visualizer scan, it displays the **Ops/s**
metric for document keys, which gives you an overview of your usage pattern.
To switch to a different metric, click the **Metric** drop-down
list above the heatmap, then click the metric you want to view.

In case of index keys, it displays the **Index Write Ops/s** metric that gives
an overview of index key usage.

For descriptions of each metric, see [Key Visualizer Metrics](https://firebase.google.com/docs/firestore/key-visualizer/key-visualizer#Metrics).

## Finding connections between different metrics for document keys

You can view multiple metrics at the same time in Key Visualizer when you want
to compare metrics or find correlations between metrics. For example, you might
want to see if hotspots on your **Ops/s** heatmap correlate with high
latency in your **Average write latency** heatmap.

To view multiple metrics and their values at the same time, click
**Show Info Panel** near the top right corner. A list of metrics appears
in a pane to the right of the scan.

![Example showing the multimetric pane for_a_scan](https://firebase.google.com/static/docs/firestore/images/keyvis-multimetric-pane.png)

To examine several metrics at once, use the following tools in the multimetric
pane:

- To show or hide miniature heatmaps for all metrics, click `Expand All` or
  `Collapse All` at the top right.

- To show an individual metric's heatmap, click the metric name.

- To hide an individual metric's heatmap, click the metric name again.

- To display a metric's heatmap in the main window, click the solid arrow at
  the left edge of the metric's title bar.

  ![Left arrow shows a metric in the main window](https://firebase.google.com/static/docs/firestore/images/keyvis-mini-metric.png)
- Hover over a miniature heatmap to see corresponding activity in the main view.

To compare different metrics for a key bucket at the same point in time, you can
pin a value in a scan, then switch to a different metric at the same point in
time:

1. Point to a position of interest on the large heatmap in the main window.
2. Click to pin the tooltip. The values in the side pane stay fixed to the key bucket and point in time you've pinned.
3. To display a metric in the large heatmap, click the solid arrow on the left for that metric. The tooltip in the main window shows you the full details for that metric.

| **Note:** Index keys provide only the **Index Write Ops/s** metric.

## What's next

- Learn to recognize [document key patterns](https://firebase.google.com/docs/firestore/key-visualizer/keyvis-patterns) or [index key patterns](https://firebase.google.com/docs/firestore/key-visualizer/keyvis-patterns-index).
- Read about the [metrics you can view in a heatmap](https://firebase.google.com/docs/firestore/key-visualizer/key-visualizer#Metrics).