# Discover Databases

> Database-centric view of every datastore your services query — throughput, errors, and latency per database, derived from the trace spans your applications already emit

Source: https://last9.io/docs/discover-databases/

The Databases feature in Discover gives you a database-centric view of every datastore your services talk to. Instead of starting from a service and drilling into its database calls, start from the database itself: see which datastores carry the most load, which are erroring, and which services drive that traffic.

![Discover Databases list view](../../../../assets/content/docs/discover/databases/databases-list-view.png)

Discover Databases is built entirely from the database client spans your instrumented services already emit — the `db.system` and `net.peer.name` attributes on spans identify each datastore. There is nothing to install on the database server.

## Prerequisites

Your services need OpenTelemetry instrumentation that records database client spans. Most language auto-instrumentations do this out of the box for common drivers. See the [database integrations](/docs/integrations/) for instrumentation guides per database and language.

If a service's database calls appear in its Traces, the databases it queries will appear here.

## Understanding the Databases View

Open **Discover → Databases** to see the datastores detected from your trace data. Last9 automatically detects databases across technologies — MySQL, PostgreSQL, MongoDB, Redis, Aerospike, and any other system that database client spans report via `db.system`.

Each row in the list shows:

| Column            | Description                                              |
| ----------------- | -------------------------------------------------------- |
| **Database Type** | The datastore technology, from the `db.system` attribute |
| **Host**          | The database host, from `net.peer.name`                  |
| **Throughput**    | Query rate per minute                                    |
| **Latency (P95)** | 95th-percentile query response time                      |
| **Error Rate**    | Percentage of failed database calls                      |
| **Services**      | Number of services querying this datastore               |

Sort by any column, or use the left-side filters to narrow by database type or host.

## Database Detail View

Click a database to open its detail view, organized into **Overview**, **Queries**, **Services**, **Infrastructure**, **Logs**, and **Traces** tabs.

![Database detail Overview tab](../../../../assets/content/docs/discover/databases/database-detail-overview.png)

The Overview tab reports:

- **Query Performance Index**: A single health score for the datastore, with summary cards for throughput, average response time, and error rate
- **Performance charts**: Query response time (AVG, P50, P90, P95, P99) and throughput over the selected range
- **Query Type Distribution**: Per-operation breakdown with throughput, average and P95 latency, and error rate
- **Top 10 Slowest Queries** and **Top 10 Most Frequent**: Each query links to its correlated traces, pre-filtered by span name, `db.system`, and `net.peer.name`
- **Top 10 Services by Load**: Which services drive the query volume — each links to that service's Database tab
- **Recent Slow Query Samples**: Actual query text from traces, with execution time

## From Database to Service and Back

Discover Databases and the per-service [Database tab](/docs/discover-services/#database) are two views of the same data:

- Start from a **service** when the symptom is service latency and you suspect a query.
- Start from a **database** when the symptom is datastore-wide — connection saturation, a slow replica, a hot table — and you need to know every service contributing load.

## Best Practices

- **Watch P95 per operation, not per database.** A healthy average hides one slow `UPDATE` path. The per-operation breakdown isolates it.
- **Use the trace pivot for slow queries.** A slow query's correlated traces show the full request context — which endpoint triggered the query and what else the request did.
- **Check fan-in before scaling up.** If one database shows load from many services, the Top Services by Load table tells you whether one consumer is responsible before you reach for a bigger instance.

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## Troubleshooting

- **A database is missing from the list**: confirm the querying service emits database client spans — open the service's Traces and look for spans with a `db.system` attribute. If the service itself is missing, see [Discover Services](/docs/discover-services/) prerequisites.

Please get in touch with us on [Discord](https://discord.com/invite/Q3p2EEucx9) or [Email](mailto:support@last9.io) if you have any questions.