What caused the sudden increase in query latency for Cockroach Labs's CockroachDB Dedicated customers in the US-East region last week?

Introduction

The sudden increase in query latency for CockroachDB Dedicated customers in the US-East region last week is a critical issue that demands immediate attention. As we dive into this analysis, we'll systematically identify potential causes, validate hypotheses, and develop a comprehensive solution strategy. Our approach will cover both technical and non-technical factors, ensuring we address the root cause while considering broader implications for our product and customers.

Step 1

Clarifying Questions (3 minutes)

• Considering the specificity of the issue, I'm wondering about the exact timing. When did we first notice the latency spike, and has it been consistent since then?

Why it matters: Pinpointing the onset helps correlate with potential triggers. Expected answer: The issue was first noticed last Tuesday and has been consistent since. Impact on approach: A sudden onset might indicate a specific event or change, while gradual increase could suggest cumulative factors.

• Given that this affects the US-East region, I'm curious about the performance in other regions. Have we seen any similar patterns elsewhere?

Why it matters: This helps determine if it's a localized issue or part of a broader trend. Expected answer: No similar patterns in other regions. Impact on approach: If isolated to US-East, we'd focus on region-specific factors; if global, we'd consider broader system changes.

• Thinking about our recent activities, have we rolled out any updates or changes to the US-East infrastructure in the past week?

Why it matters: Recent changes are often prime suspects in performance issues. Expected answer: A minor configuration update was pushed last Monday. Impact on approach: If confirmed, we'd prioritize investigating this update's impact.

• Considering user behavior, have we noticed any significant changes in query patterns or volume from our US-East customers recently?

Why it matters: Unusual user activity could strain the system in unexpected ways. Expected answer: Query volume has been stable, but there's been an increase in complex join operations. Impact on approach: This would lead us to investigate query optimization and resource allocation.

• Looking at our monitoring systems, I'm wondering if we've seen any correlated metrics spiking alongside latency?

Why it matters: Correlated metrics can provide clues about the underlying cause. Expected answer: CPU utilization on some nodes has increased. Impact on approach: This would guide us to investigate resource constraints and load balancing.