Why has the average response time for Iterable's in-app messaging API increased from 200ms to 500ms in the past 48 hours?

Introduction

The sudden increase in Iterable's in-app messaging API response time from 200ms to 500ms over the past 48 hours is a critical issue that demands immediate attention. This performance degradation could significantly impact user experience and potentially lead to customer churn. I'll approach this problem systematically, focusing on identifying the root cause, validating hypotheses, and developing both short-term fixes and long-term solutions.

Step 1

Clarifying Questions (3 minutes)

• Given the sudden spike, I'm wondering about recent deployments. Have there been any significant code changes or system updates in the past week?

Why it matters: Recent changes often correlate with performance issues. Expected answer: Yes, a new feature was deployed 72 hours ago. Impact on approach: If true, I'd focus on rollback options and code review.

• Considering the specific metric, I'm curious about traffic patterns. Has there been an unusual increase in API requests during this period?

Why it matters: Unexpected load can strain systems and increase response times. Expected answer: Traffic has remained relatively stable. Impact on approach: If traffic is stable, I'd shift focus to internal system issues.

• Looking at the timing, I'm thinking about potential data center issues. Are we seeing this increase across all regions or is it localized?

Why it matters: Helps distinguish between global system issues and localized problems. Expected answer: The issue is present across all regions. Impact on approach: A global issue would suggest a core system problem rather than a regional infrastructure issue.

• Considering the nature of in-app messaging, I'm wondering about message complexity. Has there been a change in the average size or complexity of messages being sent?

Why it matters: More complex messages could increase processing time. Expected answer: No significant change in message complexity. Impact on approach: If message complexity hasn't changed, I'd focus on system-level issues rather than data-related problems.

• Given the specific increase, I'm curious about our monitoring systems. Can we confirm that our measurement tools are functioning correctly and consistently?

Why it matters: Ensures we're addressing a real issue, not a measurement error. Expected answer: Monitoring systems have been verified and are accurate. Impact on approach: If confirmed, we can confidently proceed with root cause analysis of the actual system.