What's causing the sudden spike in latency for Criteo's real-time bidding platform?

Introduction

The sudden spike in latency for Criteo's real-time bidding platform is a critical issue that demands immediate attention. As a seasoned product leader, I'll approach this problem systematically, focusing on identifying the root cause, validating hypotheses, and developing both short-term fixes and long-term solutions.

My analysis will follow a structured framework, starting with clarifying questions to gather essential context, then moving through external factor assessment, product understanding, metric breakdown, data gathering, hypothesis formation, root cause analysis, validation planning, and finally, a comprehensive resolution strategy.

Step 1

Clarifying Questions (3 minutes)

• Looking at the timing, I'm thinking this might be a recent development. When exactly did you first notice the latency spike?

Why it matters: Pinpointing the onset helps narrow down potential causes. Expected answer: Within the last 24-48 hours. Impact on approach: A sudden onset suggests a recent change or event as the trigger.

• Considering the nature of real-time bidding, I'm wondering about the scale of the issue. What percentage of bids are experiencing this increased latency?

Why it matters: Helps determine if it's a systemic issue or affecting only a subset of transactions. Expected answer: Around 30-40% of bids are affected. Impact on approach: A widespread issue points towards core infrastructure or algorithmic problems.

• Given the complexity of the bidding system, I'm curious about any recent updates. Have there been any significant changes to the bidding algorithm or infrastructure in the past week?

Why it matters: Recent changes are often the culprit in sudden performance shifts. Expected answer: A minor update to the bidding algorithm was deployed 48 hours ago. Impact on approach: This would focus our investigation on the recent update and its potential unintended consequences.

• Thinking about external factors, I'm wondering if there's been any unusual activity from advertisers or publishers. Have you noticed any significant changes in bidding patterns or traffic volume?

Why it matters: Unusual external behavior could be straining the system. Expected answer: Traffic volume has been relatively stable, but there's been a 15% increase in bid requests from a particular ad exchange. Impact on approach: This would lead us to investigate the relationship between the increased requests and the latency spike.