How to investigate BigQuery query performance and slot usage?

PDE By islever Editorial Last updated Aug 31, 2026

Short answer

C Use available administrative resource charts to determine how slots are being used and how jobs are performing over time. Run a query on the INFORMATION_SCHEMA to review query performance.

Question

You are a BigQuery admin supporting a team of data consumers who run ad hoc queries and downstream reporting in tools such as Looker. All data and users are combined under a single organizational project. You recently noticed some slowness in query results and want to troubleshoot where the slowdowns are occurring. You think that there might be some job queuing or slot contention occurring as users run jobs, which slows down access to results. You need to investigate the query job information and determine where performance is being affected. What should you do?

Use slot reservations for your project to ensure that you have enough query processing capacity and are able to allocate available slots to the slower queries.
Use Cloud Monitoring to view BigQuery metrics and set up alerts that let you know when a certain percentage of slots were used.
Use available administrative resource charts to determine how slots are being used and how jobs are performing over time. Run a query on the INFORMATION_SCHEMA to review query performance. Correct Answer
Use Cloud Logging to determine if any users or downstream consumers are changing or deleting access grants on tagged resources.

Key Takeaways

This question tests the ability to distinguish between implementing a solution (like reservations) and performing a diagnostic investigation

To diagnose BigQuery slowness and identify slot contention, administrators should utilize administrative resource charts alongside INFORMATION_SCHEMA queries. The community consensus confirms that this combination provides the necessary visibility into job execution and resource allocation.

Common mistake: Selecting Option A is a common error because it suggests a remediation strategy (slot reservations) rather than fulfilling the specific requirement to investigate the root cause of the performance issue.

Expert Analysis

Why the Answer Is Correct

Option C is the correct choice because the question explicitly asks to "investigate" and "determine where performance is being affected." Administrative resource charts provide a high-level view of slot utilization and job performance over time, while querying the INFORMATION_SCHEMA (specifically JOBS or JOBS_BY_PROJECT) allows for a deep dive into specific query metrics, such as execution time, slot milliseconds consumed, and whether a job was queued. This two-pronged approach directly addresses the need to pinpoint bottlenecks.

Why the Other Options Are Wrong

Option A is incorrect because it proposes a configuration change (creating reservations) to solve the problem, rather than investigating the cause first. Option B involves Cloud Monitoring, which is useful for alerts but lacks the specific, detailed historical job analysis provided by the administrative charts and INFORMATION_SCHEMA for troubleshooting current slowness. Option D is irrelevant because it focuses on auditing access control changes via Cloud Logging, which has no bearing on query execution speed or slot contention.

Community Comment Notes

Community members strongly validated Option C, emphasizing that BigQuery's administrative charts are the primary tool for visualizing slot usage patterns. Additionally, comments highlighted the utility of INFORMATION_SCHEMA for retrieving detailed statistics on individual queries, which is essential for confirming if queuing is the source of the delay.

Official Reference

https://cloud.google.com/blog/topics/developers-practitioners/monitor-analyze-bigquery-performance-using-information-schema

This link opens the official vendor documentation in a new tab.

Exam Strategy

Carefully distinguish between action verbs like 'investigate' or 'troubleshoot' versus 'implement' or 'configure'. For questions requiring investigation, prioritize diagnostic tools like system views and monitoring charts over configuration changes.

Community Votes

100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

raaad 👍 10 Answered C

- BigQuery provides administrative resource charts that show slot utilization and job performance, which can help identify patterns of heavy usage or contention. - Additionally, querying the INFORMATION_SCHEMA with the JOBS or JOBS_BY_PROJECT view can provide detailed information about specific queries, including execution time, slot usage, and whether they were queued.
scaenruy 👍 1 Answered C

C. Use available administrative resource charts to determine how slots are being used and how jobs are performing over time. Run a query on the INFORMATION_SCHEMA to review query performance.
JyoGCP 👍 1 Answered C

https://cloud.google.com/blog/topics/developers-practitioners/monitor-analyze-bigquery-performance-using-information-schema
ToiToi 👍 1 Answered C

Without doubt, C!
Matt_108 👍 1 Answered C

Option C

Reader comments & corrections

No reader corrections yet — spotted an error or have a note? Share it below.

← Back to PDE Study Guide