PagerDuty Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

Software Engineers at global tech companies like PagerDuty build and maintain scalable, reliable systems that power critical digital services. Day to day, they write code, review pull requests, debug production issues, and collaborate with product and operations teams to ship features that handle high traffic and strict uptime requirements. Freshers typically start with well-scoped tasks and gradually take ownership of services or components.

Role and Technical Knowledge

1. 1

   Explain how you would design a service that sends alerts when a system metric crosses a threshold.

   Cover data ingestion, rule evaluation, notification delivery, and avoiding alert storms. Mention scalability and reliability.

2. 2

   What is the difference between a process and a thread, and why does it matter for a high-throughput server?

   Explain memory sharing, context switching, and how concurrency models affect performance and resource usage.

3. 3

   How does a load balancer work, and what algorithms can it use?

   Describe round robin, least connections, and health checks. Relate to fault tolerance and horizontal scaling.

4. 4

   Given a list of incidents with timestamps, how would you find the longest period without an incident?

   Clarify input format, sort timestamps, and compute gaps. Discuss edge cases like empty list or single incident.

Practical Scenarios

1. 5

   You deploy a new feature and see a spike in error rates. How do you debug and mitigate?

   Check logs and metrics, roll back if needed, isolate the change, and communicate with stakeholders. Emphasise blameless post-mortem.

2. 6

   A database query that was fast last week is now slow. What steps do you take?

   Check query plan, indexes, data growth, and locking. Consider caching or query optimisation.

3. 7

   How would you handle a situation where your on-call shift receives repeated false alerts?

   Tune thresholds, add suppression, and review alert rules. Balance sensitivity with noise reduction.

4. 8

   You need to add a new API endpoint that many services will call. What do you consider?

   Think about authentication, rate limiting, versioning, backward compatibility, and documentation.

Behavioural and HR

1. 9

   Tell me about a time you worked in a team to solve a difficult problem.

   Use STAR format. Highlight your specific contribution, collaboration, and the outcome.

2. 10

   Describe a situation where you received critical feedback. How did you respond?

   Show openness, action taken, and improvement. Avoid being defensive.

3. 11

   Why do you want to work in a role that involves on-call responsibilities?

   Express willingness to learn, understand the importance of reliability, and mention support systems like runbooks and escalation.

4. 12

   Where do you see yourself in three years?

   Align with growth in technical depth, ownership, and mentoring. Show commitment to learning and impact.

Coding and Problem Solving

1. 13

   Write a function to detect if a linked list has a cycle.

   Use Floyd's cycle detection. Explain time and space complexity.

2. 14

   Given an array of integers, find two numbers that sum to a target.

   Use a hash map for O(n) time. Discuss trade-offs with sorting approach.

3. 15

   Implement a stack that supports push, pop, and retrieving the minimum element in O(1) time.

   Use an auxiliary stack to track minimums. Explain why this works.

4. 16

   How would you find the kth largest element in an array?

   Discuss sorting, heap, and quickselect. Compare time and space complexity.