How do I approach Software Engineering Fundamentals interview questions?

Software Engineering Fundamentals questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master software engineering fundamentals interviews.

What difficulty level is this interview question?

This is a hard difficulty Software Engineering Fundamentals question, commonly asked during Onsite rounds at Uber.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Uber during technical interviews.

Design a Real-Time Top-K Ranking System

Quick Overview

This question evaluates a candidate's ability to design efficient in-memory data structures and APIs for a real-time Top-K ranking service, address concurrency and fault-tolerant batch processing, and outline tests for correctness and edge cases.

Design an object-oriented real-time Top-K ranking system.

The system receives score updates for many entities, such as users, drivers, restaurants, or products. Each entity has a unique ID and a numeric score. The system must support:

update(entity_id, new_score) : Insert a new entity or update the score of an existing entity.
top_k(k) : Return the k entities with the highest scores, ordered from highest to lowest. Ties should be handled deterministically, for example by sorting by entity_id ascending after score descending.
remove(entity_id) : Remove an entity from the ranking.

Requirements and follow-ups:

Propose appropriate in-memory data structures, such as a hash map plus a sorted structure.
Explain how the design changes if multiple threads call update , remove , and top_k concurrently.
Explain how to handle very large input batches where some records may be malformed or fail during processing.
Describe the tests you would write for correctness, edge cases, and concurrency.

Design a Real-Time Top-K Ranking System

Quick Overview

Solution

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