Plaid DevOps / SRE Interview Questions

1.Walk me through a time you had to rapidly deploy a monitoring or infrastructure change, then iterate on it based on what you learned. What was your v1 approach and how did you evolve it?

2.Walk me through a situation where you had to support a teammate who was struggling with an oncall rotation or incident response. What was your approach?

3.Tell me about a time you had to lead through a major incident or outage when your team was stressed or frustrated. How did you handle the human side while still driving resolution?

4.Tell me about a time you caught a potential security vulnerability or data exposure risk in your infrastructure. How did you advocate for fixing it when others wanted to move fast?

5.Describe a time when you had to choose between shipping an infrastructure change quickly versus spending more time on security or reliability hardening. What tradeoffs did you make?

6.Describe a time you built or improved an internal tool or automation for your team, then had to iterate on it based on how people actually used it. What surprised you?

7.Plaid's Auth API handles millions of bank account verifications per day. If you noticed that authentication requests to one bank were suddenly taking 5x longer than usual, how would you investigate and mitigate this?

8.You're tasked with designing monitoring for Plaid Link, the SDK that handles bank login flows for millions of users. What metrics and alerts would you implement to catch issues before they affect user conversion rates?

9.You need to implement circuit breakers for Plaid's microservices that call external bank APIs. Some banks have rate limits, others have unpredictable downtime. How would you design this system?

10.Walk me through how you'd set up blue-green deployments for a service that processes sensitive transaction data and must maintain SOC 2 compliance. What specific considerations matter for financial data?

11.Plaid's Transactions API serves categorized spending data to millions of personal finance apps. Design a caching strategy that handles both real-time transaction updates and batch category enrichment jobs.

12.Plaid handles OAuth tokens for millions of connected bank accounts. Design a token refresh system that maintains user sessions while respecting bank security policies and detecting potentially compromised credentials.

13.Plaid's Identity Verification service needs to process document uploads, run biometric checks, and query multiple identity databases within 30 seconds for a user signup flow. Design an orchestration system that can handle 10,000 concurrent verification requests while maintaining audit trails for compliance.

14.Design a deployment pipeline for Plaid's Auth API that processes millions of bank account verifications daily. The service must maintain 99.99% uptime and handle rolling deployments without dropping any verification requests during peak hours.

15.Plaid needs to migrate its transaction categorization service from a monolithic Python application to microservices to support multiple ML models and real-time category updates. Design this migration while maintaining 24/7 availability for apps that depend on transaction data.

16.Design a real-time alerting system for Plaid Protect that can detect fraudulent patterns across millions of transactions per hour and trigger immediate account freezes or step-up authentication. The system needs to balance fraud prevention with false positive rates that could block legitimate users.

17.Plaid needs to implement disaster recovery for its core banking connectivity infrastructure that handles OAuth tokens and API calls for thousands of banks. Design a multi-region system that can survive a complete AWS region failure while maintaining user sessions and bank connectivity.

18.Design a configuration management system for Plaid's microservices that can safely deploy API rate limits, feature flags, and security policies across hundreds of services. The system needs to prevent misconfigurations that could cause widespread outages or expose sensitive financial data.

19.Tell me about a time you had to convince engineers across multiple teams to adopt a new infrastructure standard or practice. What was your approach when they had competing priorities?

20.Describe a situation where you had to mentor someone on your team who was making architectural decisions that could impact reliability or security. How did you guide them without micromanaging?

21.Tell me about a time when your team was under pressure to ship something quickly, but you identified a potential issue that would require slowing down. How did you navigate that tension?

22.Walk me through a time when you had to lead your team through a significant infrastructure migration or modernization effort. How did you maintain team motivation when the work felt like it wasn't directly benefiting users?

23.Tell me about the most difficult conversation you've had with a peer or senior engineer about infrastructure practices or technical debt. What made it challenging and how did you approach it?

24.Describe a time when you had to coordinate incident response across multiple teams during a complex outage. How did you manage both the technical resolution and the human dynamics?

25.Estimate how much additional AWS cost Plaid would incur if our Link SDK conversion rate dropped by 1 percentage point. Walk me through your calculation and assumptions.

26.Estimate the number of database queries Plaid's Auth API generates per day during tax season. Assume tax apps see 10x normal usage.

27.You notice that Plaid's transaction categorization accuracy dropped from 94% to 91% over the past month, but no ML models were updated. How would you investigate this systematically?

28.Plaid processes 2 billion API calls monthly. If we reduced our average API response time by 50ms, how would you estimate the annual cost savings from reduced compute usage?

29.A bank partner just implemented stricter API rate limits that could affect 30% of Plaid's Auth requests. Estimate the potential revenue impact if this causes a 5% drop in successful verifications for affected requests.

30.Estimate how many additional customer support tickets Plaid would receive if our Link SDK error messages became 20% less helpful. Walk through your assumptions about user behavior.