Backend Engineer Interview Questions
Practice 69 real Backend Engineer interview questions for 2026 — Backend Engineer interview questions drawn from actual interviews with detailed solutions to accelerate your interview preparation. This collection focuses on the problems and decision points hiring teams actually ask: correctness and complexity in coding, API and data-model design, consistency and failure modes, performance and scaling tradeoffs, and clear behavioral stories that show ownership and impact. Expect questions that probe system thinking as much as language fluency and debugging. Companies actively hiring for backend engineers right now include Bytedance, Tesla, Harvey, and Roku, and their interview themes overlap but differ in emphasis. Bytedance and Harvey emphasize high-throughput APIs, streaming/real-time pipelines, and model-inference integration; Tesla stresses diagnostics, observability, and reliability for distributed vehicle or factory services; Roku focuses on content ingestion, metadata pipelines, and low-latency playback backends. To prepare, practice coding with complexity limits, sketch production-ready APIs and data models, review failure/recovery patterns, and rehearse concise STAR behavioral stories tied to measurable outcomes.
"I got asked a hardcore MCM DP question and I saw it on PracHub as well. Solved that question in 5 minutes. Without PracHub I doubt I could solve it in 5 hours. Though somehow didn't get hired, perhaps I guess I solved it too fast? /s"
"Believe me i'm a student here jn US. Recently interviewed for MSFT. They asked me exact question from PracHub. I saw it the night before and ignored it cause why waste time on random sites. I legit wanna go back and redo this whole thing if I had chance. Not saying will work for everyone but there is certainly some merit to that website. And i'm gonna use it in future prep from now on like lc tagged"
"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
"I was skeptical about the 'real questions' claim, so I put it to the test. I searched for the exact question I got grilled on at my last Meta onsite... and it was right there. Word for word."
"Got a Google recruiter call on Monday, interview on Friday. Crammed PracHub for 4 days. Passed every round. This platform is a miracle worker."
"I've used LC, Glassdoor, and random Discords. Nothing comes close to the accuracy here. The questions are actually current — that's what got me. Felt like I had a cheat sheet during the interview."
"The solution quality is insane. It covers approach, edge cases, time complexity, follow-ups. Nothing else comes close."
"Legit the only resource you need. TC went from 180k -> 350k. Just memorize the top 50 for your target company and you're golden."
"PracHub Premium for one month cost me the price of two coffees a week. It landed me a $280K+ starting offer."
"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Build a CSV-to-JSON Classification Service
Build a CSV-to-JSON Classification Service Build a backend service in stages. First, an HTTP request supplies a server-visible CSV path and the servic...
Design a Durable Task Scheduling Service
Design a Durable Task Scheduling Service The initial prompt is “design a task scheduler.” Begin by distinguishing an in-process timer, a durable delay...
Resolve Dependent Addition Equations
Resolve Dependent Addition Equations Problem Implement resolveEquations(equations) -> output. Each input string defines one variable as a sum of nonne...
Design Map-Based Home Search
Design Map-Based Home Search Design the backend for customers searching for homes on a map. A query supplies an arbitrary rectangular map region and m...
Critique a Recent Engineering Project and Explain What You Would Redo
Critique a Recent Engineering Project and Explain What You Would Redo Choose a meaningful engineering project from roughly the last two years. Give a ...
Find Bugs in an LRU Cache
Find Bugs in an LRU Cache The Java class below is intended to implement a least-recently-used cache. A successful get and every put should make the ke...
Implement a Synchronized First-Available Seat Allocator
Implement a Synchronized First-Available Seat Allocator Implement the core of a concurrent ticket-booking service with N seats numbered 1 through N. S...
Execute a TTL Key-Value Store with Transactions
Execute a TTL Key-Value Store with Transactions Problem Implement executeKvCommands(commands) -> outputs for an in-memory key-value store. Commands ar...
Design a Real-Time Asset Price Service
Design a near-real-time digital asset price service that evolves from one upstream provider to several. Cover normalized ingestion, source reconciliat...
Backend Fundamentals Deep Dive: MySQL Internals, Redis, and the HTTP/HTTPS Request Lifecycle
This question tests deep backend engineering knowledge across three core domains: MySQL InnoDB internals (logging, indexing, isolation), Redis persist...
Design a Distributed File System
This question evaluates design skills for large-scale distributed storage systems, testing understanding of distributed systems principles such as met...
Design Scalable Notification Rate Limiter
Design a production-grade rate limiter for notification sending that enforces limits at three levels of an organizational hierarchy. The system expose...
Evolve Cursor Pagination Without Breaking Clients
Debug bidirectional cursor pagination when many transactions share the same timestamp, then add amount sorting without breaking old clients. Define st...
Design a Thread-Safe Bounded Blocking Queue
Design a Thread-Safe Bounded Blocking Queue Design a fixed-capacity FIFO queue shared by multiple producer and consumer threads. Provide operations eq...
Debug and Improve a Load Balancer
Debug and Improve a Load Balancer Clarifying Questions to Ask - Is the load balancer a single process exercise or a distributed production service? - ...
Find the Closest Candidate String by Edit Distance
Find the Closest Candidate String by Edit Distance Problem Implement closestCandidates(candidates, queries) -> results. The edit distance between two ...
Deep-Dive a Distributed Service Project
Lead a technical deep dive into a distributed service project, connecting architecture and failure behavior to user goals, capacity, and measurable ou...
Scale Word-Frequency Processing Beyond One Machine
Design a distributed word-frequency pipeline for inputs too large for one process while preserving exact tokenization and ranking. Cover immutable obj...
Design Tennis Scoring with Pluggable Rules
Design Tennis Scoring with Pluggable Rules Prompt Design a small scoring component for one tennis game between two players. It must record which playe...
Count Lucky Numbers in an Inclusive Range
Count Lucky Numbers in an Inclusive Range Problem A positive integer x is lucky when it is divisible by floor(sqrt(x)). Implement countLuckyNumbers(le...