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Backend Engineer (on-call) simulation

Production incident: checkout is failing

Bazaarly · E-commerce marketplace1–3 yrs 20 min

You're the on-call backend engineer when checkout starts failing on the morning of a Diwali sale. Find the cause, stop the bleeding, keep people informed and make sure it doesn't happen again.

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You can pause and come back. Time in the simulation only moves when you act.

Bazaarly · Backend Engineer (on-call)Day 1 · 09:00 AM

Your first message

MonitoringAlerting system09:00 AM

SEV-2: checkout-api error rate 6.2%, p95 4.2s

checkout-api error rate is 6.2% (threshold 2%) and p95 latency is 4.2s. The sale's traffic peak starts at 11:00 AM. You are the on-call engineer. What's your first move?

Your objective

Restore checkout before the 11:00 AM traffic peak, keep support and leadership informed, and prevent a repeat.

Your day

What's scheduled. More will come up depending on what you do.

  1. 09:00 AMSEV-2: checkout-api error rate 6.2%, p95 4.2s · Monitoring
  2. 09:20 AMCustomers can't check out. What do I tell them? · Arjun Das
  3. 09:55 AMFound the cause · Rohan Mehta

Before you start

  • It's 9:00 AM on the first day of the Diwali sale. Peak traffic starts at 11:00 AM.
  • You're on call for checkout-api this week. Rohan (SRE) is your on-call partner.
  • Everything in this company is fictional. Data, logs and people react to what you do.
  • Reply in your own words, the way you would at work. There are no multiple-choice answers.

You'll work in

Gmail Slack Drive Datadog

Each app is laid out like the tool most teams in this role use. Simverse isn't affiliated with these companies.

People you'll work with

  • Rohan Mehta · SRE, on-call partner
  • Priya Raman · Engineering Manager
  • Neha Kulkarni · Product Manager, Checkout
  • Arjun Das · Customer Support Lead
  • Vikram Sethi · CTO

What's assessed

  • Problem understanding

    Works out what is actually required, including constraints and unstated edge cases.

  • Problem solving

    Forms hypotheses and makes evidence-based decisions instead of random changes.

  • Coding

    Writes correct, readable, proportionate code that meets the requirements.

  • Debugging

    Finds the root cause from evidence, recovers from failures and verifies the fix.

  • Testing

    Verifies work with tests, covers edge cases and catches regressions.

  • Adaptability

    Changes approach when the evidence says so and responds to new information.

  • Autonomy

    Makes progress independently and uses hints and AI with judgment and verification.

  • Communication

    Explains reasoning, decisions and trade-offs clearly.