What caused the sudden 30% increase in failed Interac Debit transactions at grocery stores last weekend?

Introduction

The sudden 30% increase in failed Interac Debit transactions at grocery stores last weekend is a critical issue that demands immediate attention. This analysis will systematically identify, validate, and address the root cause while considering both short-term and long-term implications for our product and users.

I'll approach this problem by first clarifying key details, ruling out external factors, and then diving deep into our product ecosystem. We'll break down the metric, gather relevant data, form hypotheses, and conduct a thorough root cause analysis. Finally, we'll develop a comprehensive plan to validate our findings and implement solutions.

Step 1

Clarifying Questions (3 minutes)

• Looking at the timing, I'm thinking this could be related to a recent system update. Has there been any significant changes to our payment processing system in the past week?

Why it matters: System changes often correlate with performance issues. Expected answer: Yes, a minor update was pushed last Tuesday. Impact on approach: If confirmed, we'd focus on the update's components and rollout process.

• Given the specific mention of grocery stores, I'm wondering if this is isolated to a particular merchant category. Are we seeing similar increases in failed transactions across other merchant types?

Why it matters: Helps determine if this is a global issue or specific to grocery transactions. Expected answer: No, other merchant categories seem unaffected. Impact on approach: We'd investigate grocery-specific transaction characteristics or integrations.

• Considering the 30% increase, I'm curious about the baseline. What's our typical failure rate for Interac Debit transactions at grocery stores?

Why it matters: Establishes the severity of the issue relative to normal operations. Expected answer: Usually around 2-3% failure rate. Impact on approach: A jump from 2-3% to 32-33% would indicate a severe problem requiring immediate action.

• Thinking about potential data anomalies, has there been any change in how we're measuring or reporting failed transactions recently?

Why it matters: Ensures we're dealing with a real issue, not a reporting error. Expected answer: No changes to measurement or reporting systems. Impact on approach: If there were changes, we'd need to audit our data collection and reporting processes first.