What's causing the sudden increase in origin shield failures for customers using Fastly's Compute@Edge platform?

Introduction

The sudden increase in origin shield failures for customers using Fastly's Compute@Edge platform is a critical issue that demands immediate attention. This problem could significantly impact our customers' performance and reliability, potentially leading to service disruptions and dissatisfaction. In addressing this issue, I'll follow a systematic approach to identify, validate, and address the root cause while considering both immediate and long-term implications.

I'll begin by clarifying the problem's scope and context, then rule out basic external factors. Next, I'll dive into product understanding, metric breakdown, and data gathering. From there, I'll form hypotheses, conduct root cause analysis, and propose validation methods and next steps. Finally, I'll present a decision framework and resolution plan.

Step 1

Clarifying Questions (3 minutes)

• Given the sudden nature of the increase, I'm wondering about recent changes. Have there been any significant updates to the Compute@Edge platform in the past week or two?

Why it matters: Recent changes could be directly related to the origin shield failures. Expected answer: Yes, there was a minor update to the platform's caching logic. Impact on approach: If confirmed, I'd focus on investigating the update's impact on origin shield functionality.

• Considering the complexity of our system, I'm curious about the scope. Is this issue affecting all customers equally, or are we seeing variations across different customer segments or regions?

Why it matters: Understanding the distribution helps narrow down potential causes. Expected answer: The issue seems more prevalent among customers with high-traffic applications. Impact on approach: I'd prioritize investigating factors that disproportionately affect high-traffic scenarios.

• Thinking about our monitoring systems, I'm wondering about the detection timeline. When exactly did we first notice this increase in origin shield failures?

Why it matters: The timing could reveal correlations with other events or changes. Expected answer: The issue was first detected about 48 hours ago. Impact on approach: I'd focus on events and changes within a 72-hour window around the detection time.

• Considering the nature of origin shield failures, I'm curious about the failure patterns. Are we seeing consistent failure rates or intermittent spikes?

Why it matters: The pattern of failures can indicate whether it's a systemic issue or triggered by specific conditions. Expected answer: We're observing intermittent spikes during peak traffic hours. Impact on approach: I'd investigate factors that could be exacerbated during high-load periods.