Monitor Slow Queries and Wait Events with Datadog DBM (2026)

Datadog’s Database Monitoring (DBM) service doesn’t just tell you that your queries are slow; it pinpoints why by correlating query performance with the actual wait events happening inside your database.

Let’s watch DBM in action. Imagine a PostgreSQL database. We’ve got our pg_stat_statements extension enabled, and Datadog’s agent is collecting metrics.

Here’s a snippet of a pg_stat_statements output, showing a query that’s taking a while:

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This shows the query text, how many times it ran (calls), and the total time spent (total_time). But what made it slow? That’s where DBM shines.

When you drill into this query in Datadog’s DBM UI, you’ll see a breakdown of the time spent, not just in CPU or I/O, but specifically in database wait events. These are the moments the database engine is pausing, waiting for something.

For example, you might see a significant amount of time spent in a Lock wait event. This means your query was trying to access data that another transaction had locked, and it had to wait for that lock to be released.

Or, you might see IO_WAIT or BufferPin events. IO_WAIT is straightforward: the database is waiting for data to be read from or written to disk. BufferPin is more nuanced; it means the database is waiting for a data block in memory (the buffer cache) to be available, often because it’s being written out or needs to be read from disk first.

The Core Problem: DBM connects the abstract "slowness" of a query to the concrete, internal mechanisms of the database engine. It bridges the gap between "my application is slow" and "PostgreSQL is waiting for disk I/O on block X because transaction Y holds a lock on it."

How DBM Works Internally

1. Agent Collection: The Datadog Agent, running on your database host or a dedicated machine, connects to your database using standard drivers. It’s configured to collect both query performance metrics and database internal metrics.
2. Query Performance: For supported databases (PostgreSQL, MySQL, SQL Server, Oracle, etc.), DBM leverages built-in performance views and extensions.
   • PostgreSQL: pg_stat_statements is crucial. The agent periodically queries this view to get aggregated statistics about query execution (calls, total time, rows returned, etc.).
   • MySQL: performance_schema is the primary source, specifically tables like events_statements_summary_by_digest and events_waits_summary_global_by_event_name.
   • SQL Server: DMVs like sys.dm_exec_query_stats, sys.dm_os_wait_stats, and sys.dm_exec_requests are used.
3. Wait Event Collection: This is where DBM really differentiates itself. It doesn’t just look at query statistics; it looks at what the database was doing when it wasn’t executing code.
   • PostgreSQL: The agent can be configured to sample pg_stat_activity more frequently, or in some cases, leverage extensions that expose wait event information directly. DBM also correlates query plans with wait events.
   • MySQL: performance_schema is rich with wait event data (events_waits_summary_global_by_event_name). The agent aggregates this.
   • SQL Server: sys.dm_os_wait_stats provides a global view, and sys.dm_exec_requests can show current waits per session, which DBM samples.
4. Correlation: The magic happens in Datadog’s backend. The aggregated query performance data is enriched with the sampled wait event data. DBM uses query digests (normalized query fingerprints) to link specific queries to the dominant wait events occurring during their execution. It can also infer wait events from query execution plans.
5. Visualization: The DBM UI then presents this correlated data. You see a list of slow queries. When you click on one, you get a detailed breakdown, including:
   • Execution Plan: How the database intended to run the query.
   • Wait Events: A breakdown of the time spent waiting, categorized by type (e.g., Lock, IO_WAIT, CPU, Network).
   • Resource Usage: CPU, memory, I/O, network metrics from the host.
   • Query Metrics: Rows fetched, execution count, average duration.

The Levers You Control

• Agent Configuration: You control how frequently the Datadog agent samples database activity. Higher sampling rates provide more granular data but increase agent overhead. For PostgreSQL, enabling pg_stat_statements with track_utility = off and appropriate max settings is key.
• Database Configuration: Ensure necessary extensions (pg_stat_statements for PG) are enabled and configured. For MySQL, performance_schema needs to be enabled.
• Alerting Thresholds: In Datadog, you set alerts based on query duration, execution count, or specific wait event percentages. For example, you might alert if a query takes longer than 5 seconds and more than 30% of its execution time is spent on Lock waits.
• Tagging: Proper tagging of your database hosts and DBM integrations in Datadog allows you to filter and analyze performance by environment (dev/staging/prod), application, or region.

The Counterintuitive Truth About Wait Events

Many engineers think of "slow queries" as purely an application code or indexing problem. While those are often true, the database itself spends a significant amount of its "slowness" waiting. These aren’t necessarily errors; they are the inherent, observable states of the database engine managing concurrent access, I/O, and resource contention. DBM’s power lies in making these internal, passive states visible and directly attributable to the active queries that cause or exacerbate them, turning abstract delays into actionable diagnostics.

When you fix the identified wait events, you’ll often encounter a new set of metrics in your database, potentially related to increased cache hit ratios or reduced transaction contention.