10+ Senior Backend Developer Interview Questions and Answers

Design an admin dashboard for Uber to display driver metrics like availability over an area.

• Include a map showing driver locations in real-time

• Display driver availability status (online/offline) with color-coded indicators

• Show driver metrics such as total number of drivers, average wait time, and busiest areas

• Allow filtering by specific areas or time periods

• Provide analytics and insights based on driver data

Use binary search to identify odd weight ball among similar balls with minimum steps

• Divide the balls into two equal halves and weigh them

• If one side is heavier, repeat the process with that side

• If both sides are equal, the odd weight ball is among the unweighed balls

Use array method to extract details about an array of strings

• Use the map method to extract specific details from each element in the array

• For example, use map to extract the length of each string in the array

• Another example is to use map to convert all strings to uppercase

Serial and parallel streams in Java are used for processing collections of data in a sequential or parallel manner.

• Serial streams process elements in a single thread, while parallel streams use multiple threads for faster processing.

• Parallel streams can improve performance for large datasets by utilizing multiple cores of the processor.

• Serial streams are suitable for smaller datasets or when order of processing is important.

• Use parallel streams with caution as they may introd...read more

Fibonacci sequence can be generated using recursion, where each number is the sum of the two preceding ones.

• Basic Definition: The Fibonacci sequence starts with 0 and 1, and each subsequent number is the sum of the previous two.

• Recursive Function: A simple recursive function can be defined as follows: `function fibonacci(n) { return n <= 1 ? n : fibonacci(n - 1) + fibonacci(n - 2); }`.

• Base Cases: The recursion has two base cases: `fibonacci(0) = 0` and `fibonacci(1) = 1`.

• Perf...read more

System design for skyscanner

• Use microservices architecture for scalability

• Implement caching to improve performance

• Utilize a distributed database for handling large amounts of data

• Use load balancing to distribute traffic evenly

• Implement a robust search algorithm for accurate results

Concurrent API calls happen when multiple requests are made simultaneously, allowing for faster processing.

• Concurrent API calls can be achieved using asynchronous programming techniques such as callbacks, promises, or async/await.

• API calls can be made in parallel or in sequence, depending on the requirements of the application.

• Tools like Axios or Fetch API in JavaScript can be used to make concurrent API calls.

• Concurrency can improve the performance of an application by reduc...read more

A session is a temporary state stored on the server, while Redis is an in-memory data structure store often used for session management.

• Session Management: Sessions are used to store user-specific data (like login status) across multiple requests, enhancing user experience.

• Redis as a Session Store: Redis is commonly used to store session data due to its fast read/write capabilities and support for data expiration.

• In-Memory Storage: Redis stores data in memory, allowing for qu...read more

Design a web scale web crawler for efficient and effective data retrieval.

• Utilize a distributed architecture to handle large amounts of data and parallel processing.

• Implement intelligent crawling strategies to prioritize important pages and avoid duplicate content.

• Use efficient data storage and indexing techniques to manage the crawled data effectively.

• Consider scalability, fault tolerance, and monitoring for a robust web crawler system.

Advanced concepts in Node.js include event loop, streams, clustering, worker threads, and async/await.

• Event loop: Node.js uses a single-threaded event loop to handle asynchronous operations.

• Streams: Node.js streams allow for efficient processing of data in chunks.

• Clustering: Node.js clustering allows for scaling applications across multiple CPU cores.

• Worker threads: Node.js supports worker threads for parallel processing of tasks.

• Async/await: Async/await syntax simplifies han...read more

Snake game is a classic arcade game where a player controls a snake to eat food and grow longer while avoiding collisions with walls and itself.

• Create a grid-based game board where the snake can move in four directions (up, down, left, right)

• Generate food randomly on the board for the snake to eat and grow in length

• Implement collision detection to check if the snake hits the walls or itself

• Update the game state continuously based on user input and game logic

• Keep track of the ...read more