Triesmedium45 minBackend Engineer

Inventory Prefix Intent Index

Backend Engineer signal: trie + prefix counts in a flash-sale inventory context. This is a ProdMatch-owned backend engineer drill, framed as a May 2026 Arcesium Marketplace Infra simulation, not a copied platform question.

Company context

Arcesium · Marketplace Infra

Freshness

May 2026

Product surface

flash-sale inventory

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

Question

Build a prefix index for flash-sale inventory. Support insert(term, weight), delete(term), and topPrefix(prefix) returning the best active term by weight then lexicographic order.

Input

A sequence of index operations.

Output

Return values for topPrefix operations.

Constraints

1 <= operations <= 200000
Total characters <= 1000000
Weights can change through reinsertion.

Concepts

idempotency
queues
rate limiting
trie
prefix counts
autocomplete

insert pay 5, insert payout 7, topPrefix pa -> payout

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

Deletion is hard if nodes cache best child; use lazy invalidation or per-node heap when deletes are frequent.
Tie-break lexicographically for deterministic output.

Next Similar Problems

Idempotency Prefix Intent Indexhard Ledger Prefix Intent Indexmedium Courier Prefix Intent Indexmedium