Top Low Level Design Round Interview Questions Asked in 2026

Design Parking Lot should still be the first question in your 2026 LLD list. It continues to appear very frequently in public interview experiences and LLD question databases.

A parking lot can have multiple floors. Its core features will be:

• park and unpark vehicles,
• search parked vehicles by vehicle number,
• count the number of free spots on a given floor for a given vehicle type.

Your entities will include a ParkingLot class, which will contain a list of ParkingFloor(s). ParkingFloor will contain a 2-D array of ParkingSpot(s) arranged in rows and columns.

There can be multiple parking strategies, so we should use the strategy design pattern to solve this question.

LRU cache and its variants, like LFU cache, cache with TTL, etc., have been asked frequently as well. Almost every company has asked them.

This question is more of a DSA-based design question and has appeared frequently during low level design rounds.

Implement a RateLimiter class with an isAllowed method. Requests will be made to different resourceIds. Each resourceId will have a strategy associated with it.

There are the following strategies. Assume 1 time unit == 1 second.

1. fixed-window-counter: Fixed Window Counter divides time into fixed blocks, like 1 second, and tracks a request count per block. If the count exceeds the limit, new requests are blocked. It is fast and simple but can allow burst behavior at window boundaries.

2. sliding-window-counter: Sliding Window, log-based, stores timestamps of recent requests and removes those outside the window for each new request. If the number of remaining requests is still within the limit, the request is allowed. Otherwise, it is blocked. It provides accurate rate limiting but requires more memory and processing.

Write code for the low level design of a movie ticket booking system like BookMyShow.

The system has cinemas located in different cities. Each cinema will have multiple screens, and users can book one or more seats for a given movie show.

The system should be able to add new cinemas and movie shows in those cinemas.

Users should be able to list all cinemas in their city that are displaying a particular movie.

For a given cinema, users should also be able to list all shows that are displaying a particular movie.

Design a lightweight expense-sharing system that tracks how much each person owes or is owed after group expenses are split evenly among participants. The system maintains net balances and exposes operations to add users, record expenses, and list simplified debtor-to-creditor balances.

Microsoft especially frequently asks elevator-based questions.

We are talking about a smart elevator system found in large office buildings. This is actually a difficult question. Its core features are:

• track the state of lifts, i.e., the floor the lift is at, move direction, number of passengers, and existing and future requests,
• assign a lift optimally to a user who is on a given floor and wants to go to a destination floor.

A lift in an elevator system can be in one of three states: Moving Up, Moving Down, and Idle.

In each state, it will behave differently while taking decisions like whether to stop on a floor, add a new request or not, etc.

We will use the state design pattern to solve this problem.

These questions use the observer design pattern in their solution.