Graphshard70 minPlatform Engineer

Registry Dependency DAG Recovery

Platform Engineer signal: topological sort + cycle detection in a service registry context. This is a ProdMatch-owned platform engineer drill, framed as a March 2026 Ola Internal Platform simulation, not a copied platform question.

Company context

Ola · Internal Platform

Freshness

March 2026

Product surface

service registry

ProdMatch interview simulation based on product-team patterns; not a claim of a real company question.

Question

You own service registry for a Platform Engineer loop. Given services and directed dependencies between them, return a valid execution order. If a cycle exists, return an empty list and identify that the rollout is blocked.

Input

n nodes labelled 0..n-1 and dependency pairs [before, after].

Output

A valid order of all nodes, or [] when dependencies contain a cycle.

Constraints

1 <= n <= 200000
0 <= dependencies.length <= 400000
The graph may be disconnected.

Concepts

build DAGs
tenant quotas
artifact caching
topological sort
cycle detection
dependency graph

services: 4, deps: [[0,1],[0,2],[2,3]] -> [0,1,2,3] or [0,2,1,3]

Approach

Try framing your own approach first. The 30 seconds you think before peeking is where learning happens.

Clean Solution

Reveal the approach first.

How well did you understand?

Your rating tunes when this problem shows up again.

Common Mistakes

Mark visited when enqueueing, not after repeated dequeue.
Do not ignore disconnected components if the product surface can have them.

Next Similar Problems

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