Ola

Role: SDE 2

College: Not Specified

Interview Date: July 2024

Interview Type: Not Specified (likely virtual, all rounds on one day)

Result: Selected (Offer)

Difficulty: Medium-Hard

Rounds: 3 rounds

Topics Asked: Data Structures & Algorithms (DP, Sliding Window, Number of Islands), System Design (URL Shortening Service, Ola's internal notification system), Object-Oriented Programming (SOLID principles), Behavioral, Project Discussion.

Experience:

This candidate applied for an SDE 2 role at Ola after seeing a LinkedIn post and received an offer. The entire interview process, consisting of three eliminatory rounds, was completed in a single day.

Round 1: Problem-Solving (DSA-Based) - 60 Mins

• The interviewer, a Senior SDE, started with introductions and questions about the candidate's current work.
• A standard Dynamic Programming (DP) problem was asked. The candidate first provided a brute-force approach, then an optimized solution, and wrote the code with a dry run.
• The interviewer was helpful when the candidate got stuck.
• Another problem involved strings and the sliding window technique (exact question not remembered).
• The classic Number of Islands problem was also asked.
• Follow-up: Modify the code to calculate the area of the largest island.

Round 2: High-Level Design (HLD) - 90 Mins

• The interviewer was an Engineering Manager.
• Questions about the candidate's team and most challenging work.
• Design Ola's internal notification system. Expectations included HLD, LLD components, skeleton code, APIs, and DB schemas.
• The interviewer grilled the candidate with multiple scenarios during the design discussion.
• Another design question was to design a URL Shortening Service, covering aspects like short URL length, database choice, storage of URLs, caching (eviction policies, write strategies), URL expiry and cleanup, and tracking access counts.

Round 3: Hiring Manager - 45 Mins

• The interviewer was a Senior HR.
• Brief introductions.
• Questions about current role and work experience.
• Technical questions on SOLID principles, explaining each with code snippets.
• Puzzle: A census taker and a woman with three children. Product of ages is 72, sum is the house number 14. After initial calculations, the census taker needs more information. The woman adds, "I need to check on my eldest child who is ill." Determine the ages of the children. (Candidate found two sets and but couldn't confidently pick one).
• Behavioral questions.
• Discussion on expected compensation and joining date.