Intervalshard70 minBackend Engineer

Idempotency Capacity Interval Planner

Backend Engineer signal: line sweep + interval merge in a payment idempotency context. This is a ProdMatch-owned backend engineer drill, framed as a April 2026 Uber Payments Core simulation, not a copied platform question.

Company context

Uber · Payments Core

Freshness

April 2026

Product surface

payment idempotency

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

Question

Plan capacity for payment idempotency. Given reservation intervals with requested units, return the minimum capacity needed and all time ranges where capacity crosses a critical threshold.

Input

Intervals [start, end, units] and threshold.

Output

Peak capacity and merged high-pressure intervals.

Constraints

1 <= intervals.length <= 200000
Intervals are half-open: [start, end).
Timestamps fit in signed 32-bit integers.

Concepts

idempotency
queues
rate limiting
line sweep
interval merge
capacity planning

[[1,4,3],[2,5,4]], threshold=6 -> peak=7, hot=[[2,4]]

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?

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Common Mistakes

Be explicit about whether touching endpoints overlap.
Process end events before start events for half-open intervals.

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