Heap / Priority Queuehard70 minData Engineer

Metrics Real-Time Top-K Prioritizer

Data Engineer signal: heap + top-k in a metric dependency graph context. This is a ProdMatch-owned data engineer drill, framed as a April 2026 Unacademy Analytics Platform simulation, not a copied platform question.

Company context

Unacademy · Analytics Platform

Freshness

April 2026

Product surface

metric dependency graph

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

Question

Your Analytics Platform team needs a live top-k view for metrics. Each update changes an item's score. Return the current top k item IDs after each update, ordered by score desc then ID asc.

Input

Initial scores, k, and update stream [id, delta].

Output

Top-k IDs after every update.

Constraints

1 <= items <= 200000
1 <= updates <= 200000
Scores can be negative.

Concepts

stream windows
watermarks
lineage DAGs
heap
top-k
streaming rank

scores: [5,1,3], k=2, update [1,+5] -> [1,0]

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

Use a stable tie-breaker for equal scores.
Do not sort the full stream when k is small.

Next Similar Problems

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