What caused the sudden spike in transaction failures for LinkAja's QR code payments yesterday afternoon?

Introduction

The sudden spike in transaction failures for LinkAja's QR code payments yesterday afternoon is a critical issue that demands immediate attention and thorough analysis. As we delve into this problem, we'll employ a systematic approach to identify, validate, and address the root cause while considering both short-term fixes and long-term implications for the product.

I'll begin by gathering essential information, analyzing potential causes, and developing data-driven hypotheses. From there, we'll prioritize our findings, validate our assumptions, and create a comprehensive plan to resolve the issue and prevent future occurrences.

Step 1

Clarifying Questions (3 minutes)

• Looking at the timing, I'm thinking this could be related to a recent deployment. Have there been any system updates or changes implemented in the past 24-48 hours?

Why it matters: Recent changes often correlate with sudden performance issues. Expected answer: Yes, a minor update was pushed yesterday morning. Impact on approach: If confirmed, we'd focus on rollback options and code review.

• Considering the specificity of QR code payments, I'm wondering about the scope. Is this issue affecting all QR code transactions or only a specific subset of users or merchants?

Why it matters: Helps narrow down potential causes and affected user segments. Expected answer: The issue seems to be affecting about 60% of QR code transactions across all user types. Impact on approach: A widespread issue suggests a core system problem rather than a localized one.

• Given the sudden nature of the spike, I'm curious about any unusual traffic patterns. Have you noticed any significant changes in transaction volume or user behavior leading up to the failure spike?

Why it matters: Unusual activity could indicate external factors or potential security issues. Expected answer: Transaction volume was within normal ranges, but there was a slight increase in new user registrations. Impact on approach: If confirmed, we'd investigate potential connections between new users and the failure rate.

• Considering the critical nature of payment systems, I'm thinking about redundancy. Are there any backup systems or failover mechanisms that should have prevented this issue?

Why it matters: Helps assess the robustness of the current system and identify potential points of failure. Expected answer: Yes, we have redundant systems, but they didn't engage as expected. Impact on approach: This would lead us to investigate the failover mechanisms and their triggers.

• Reflecting on the broader ecosystem, I'm wondering about dependencies. Have there been any reported issues with third-party services or APIs that LinkAja relies on for QR code payments?

Why it matters: External dependencies can often be the source of unexpected issues. Expected answer: No reported issues from our main payment processing partners. Impact on approach: This would shift our focus more towards internal systems and processes.