Incident · advanced · 30 min · Premium

Intermittent timeouts, no source access

Northwind's claims assistant is timing out for a third of customers and you cannot read their code. Contain it from the console, find the phase that is slow, commit to a root cause, and write the first status update.

Brief

Customer: Northwind Insurance (synthetic customer; every metric, trace and log in this incident is made up for the exercise)
Situation: 09:41. Northwind's on-call paged you: claims-assistant: 5xx/timeout rate 31% for 12 min, customers seeing 'request timed out'. Northwind runs the assistant on their side; you have the operator console for the deployment you delivered, the logs and the router, and no access to their application code. The product lead is on the bridge asking for a cause and an ETA.
Your role: You are the FDE on call for the Northwind deployment. Contain first, then diagnose, then say what you know. The console is live: the topology, traces, metrics and logs are the same system your commands read. answer commits your diagnosis; a wrong commit is recorded, not fatal.
Goal: Get the gateway's timeout rate under 5% without waiting for the provider to recover, name the slow phase from the timings rather than from a guess, commit to the root cause, and write the status update the bridge is waiting for.

Objectives

1.Contain the impact: gateway timeouts under 5% without waiting for the provider
2.Commit to the root cause (you commit to an answer)
3.Write the status update the bridge is waiting for: impact, cause, containment, next step, owner

You will practise

→Contain before you diagnose: use the lever that stops customer impact
→Locate a slow phase from client and server timings without reading the code
→Distinguish provider latency from gateway, runtime and downstream causes
→Write a status update with cause, containment, customer impact and next step

The mechanism, explained

Intermittent timeouts with no access to the customer's code
the interview question this incident is built from: what you can measure from outside
p50, p95, p99 and tail latency
why a healthy p50 and a broken p95 are the signature of this incident
Fallbacks and provider failover
the containment lever, and what it costs on the fallback's limits
AI incident response
the status-update shape: impact, cause, containment, next step, owner

Do first

Give the agent a stop rule

Mission workspace

This mission is part of premium, with every challenge and incident in the lab. The brief above is the whole problem; the box, the hints and the debrief are what you unlock.

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