Graphshard70 minData Engineer

Backfill Evidence Path Finder

Data Engineer signal: shortest path + weighted graph in a incremental backfill context. This is a ProdMatch-owned data engineer drill, framed as a May 2026 Pine Labs Data Reliability simulation, not a copied platform question.

Company context

Pine Labs · Data Reliability

Freshness

May 2026

Product surface

incremental backfill

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

Question

In incremental backfill, entities are connected by weighted evidence edges. For each query, find the least-cost evidence path from source to target while avoiding blocked entities.

Input

Weighted graph, blocked set, and q source-target queries.

Output

Minimum cost per query, or -1 if unreachable.

Constraints

1 <= nodes <= 100000
1 <= edges <= 300000
1 <= queries <= 100000
All weights are non-negative.

Concepts

stream windows
watermarks
lineage DAGs
shortest path
weighted graph
retrieval quality

0-1 cost 2, 1-2 cost 3, query 0->2 -> 5

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

Watermark Dependency DAG Recoverymedium Watermark Evidence Path Finderhard Lineage Dependency DAG Recoveryhard