Amazon technical phone screen interview

Questions Amazon asks in this round 130

• 

  Tell me about a time you met a tight deadlineBehavioralDescribe a project with a deadline that was hard to meet. Say when you saw the plan was at risk, what you personally did (cut scope, re-plan, ask for help), how you told…

  Last asked Sep 2026Were you asked this too?
• 

  Tell me about a time you went beyond your responsibilitiesBehavioralDescribe a time you took on a problem nobody had assigned to you: an inefficient team process you fixed, a tool that helped teams beyond your own, a risky project you owned end to…

  Last asked Sep 2026Were you asked this too?
• 

  Tell me about a time you dove deep to find a root causeBehavioralDescribe a hard problem you had to investigate in depth, such as an intermittent failure where the obvious metrics looked healthy. Walk through the symptom, the hypotheses you…

  Last asked Sep 2026Were you asked this too?
• 

  Course schedule: finish every course and find an orderCodingYou have n courses and a list of prerequisite pairs. 1. Decide whether every course can be completed. This fails exactly when the prerequisites contain a cycle. 2. Return one…

  Last asked Jul 2026Were you asked this too?
• 

  Tell me about a time you overcame a major obstacleBehavioralDescribe a time an unexpected obstacle threatened an important goal. Explain what the obstacle was, your role, the options you weighed, what you did, and how it turned out. Expect…

  Last asked Oct 2026Were you asked this too?
• 

  Tell me about a time you learned something new to solve a problemBehavioralDescribe a problem you did not know how to solve at first, or a time you stepped outside your comfort zone, and how you learned what you needed: a new technology, domain or skill…

  Last asked Sep 2026Were you asked this too?
• 

  Top K frequent elementsCodingGiven an integer array and k, return the k values that occur most often, in any order; ties at the cutoff may go either way. One version asks for the most frequent request IDs in…

  Last asked Sep 2026Were you asked this too?
• 

  Tell me about a time you improved things for a customerBehavioralDescribe a customer pain point you noticed and acted on, or a time you judged how good the customer experience really was. Explain how you learned what the customer needed, what…

  Last asked Oct 2026Were you asked this too?
• 

  Concatenated wordsCodingGiven a list of distinct words, return every word that can be split into two or more pieces that are each a word in the list (the same word may be used more than once). A shorter…

  Last asked Oct 2026Were you asked this too?
• 

  Lowest common ancestor in a binary search treeCodingGiven a binary search tree and two distinct keys that are both in it, return their lowest common ancestor: the deepest node whose subtree contains both. A node's subtree includes…

  Last asked Sep 2026Were you asked this too?
• 

  Tell me about a time you got critical feedbackBehavioralDescribe a time you received negative or critical feedback. Explain what the feedback was, how you reacted, what you changed, and how you showed the improvement, ideally with…

  Last asked Sep 2026Were you asked this too?
• 

  Design an AI chatbot appAI systemBuild a chatbot app on top of a hosted LLM API: conversations, streamed answers, history, and per-user usage limits.

  Last asked Aug 2026Were you asked this too?
• 

  Tell me about a time you worked through ambiguityBehavioralDescribe a project where the requirements were unclear. Explain how you made progress anyway: what you clarified, what assumptions you made and checked, how you kept stakeholders…

  Last asked Aug 2026Were you asked this too?
• 

  Meeting rooms: attend all, rooms needed, busiest roomCodingGiven meetings as start and end times: 1. Can one person attend every meeting? 2. What is the fewest rooms needed to hold all of them? 3. With a fixed number of rooms and a rule…

  Last asked Aug 2026Were you asked this too?
• 

  Track missing package IDs from out-of-order arrivalsCodingPackages with IDs 1, 2, 3, ... arrive in any order. Support recording an arrival, reporting the contiguous frontier (the largest ID such that every ID up to it has arrived), and…

  Last asked Aug 2026Were you asked this too?
• 

  Stable softmax and multi-head attention in NumPyCodingIn NumPy, implement a numerically stable sigmoid and softmax, then scaled dot-product attention, then multi-head attention from scratch.

  Last asked Jul 2026Were you asked this too?
• 

  Design a library management systemOO designModel books, copies, members, loans, holds and fines for a library, with search and limits on loans per member.

  Last asked Jun 2026Were you asked this too?
• 

  Count connected components in an undirected graphCodingGiven n nodes and a list of undirected edges, return the number of connected components. It was also asked with products: each pair says two products are in the same category, and…

  Last asked May 2026Were you asked this too?
• 

  In-memory pub/sub with prioritiesOO designDesign and code a publish/subscribe system that runs on one machine: topics, subscribing, unsubscribing and publishing. Follow-up: messages carry a priority and higher-priority…

  Last asked Apr 2026Were you asked this too?
• 

  Detect a cycle in a directed graphCodingDecide whether a directed graph contains a cycle, using depth-first search with node states or Kahn's topological sort. Variants that came up: start with a linked list (fast and…

  Last asked Oct 2025Were you asked this too?
• 

  Cloud infrastructure: VPC layout, IP planning and central managementSystem designA support-engineering screen of cloud infrastructure questions: how would you lay out a VPC with several tiers? With 2,000 servers, how many IP addresses and what CIDR blocks do…

  Possibly retiredWere you asked this too?
• 

  Memory usage switcher with configurable thresholdsOO designDesign and code an in-memory switcher that watches memory usage and switches between states (or targets) when usage crosses thresholds the caller can configure. Cover how…

  Possibly retiredWere you asked this too?
• 

  Report a user's license usage from a log fileCodingWrite a command-line script called as ./script.sh <username <logfile. Each log line looks like timestamp license user@hostname. Print the result the interviewer asks for about…

  Possibly retiredWere you asked this too?
• 

  Sort characters by frequencyCodingGiven a string, rearrange it so the most frequent characters come first, each character's copies kept together. Count with a hash map, then sort or bucket by count.

  Possibly retiredWere you asked this too?
• 

  Unique visitors per department from click logsCodingEach product has an id, a department, a category and a subcategory; the last three form a parent-child hierarchy. A click log records (customerid, productid). For any department…

  Possibly retiredWere you asked this too?
• 

  AI-agent security detection over streaming telemetryAI systemDesign a system in which an AI agent reads a stream of security telemetry and runs detections on it. About 1 TB of data arrives per day. It was asked like a traditional system…

  Last asked Oct 2026Were you asked this too?
• 

  Find every recipe you can make from your suppliesCodingYou have an unlimited stock of some basic supplies and a book of recipes. Each recipe has a unique name and a list of ingredients; an ingredient can be a supply, the name of…

  Last asked Oct 2026Were you asked this too?
• 

  Minimum time to finish dependent steps run in parallelCodingA job is split into n steps numbered 0 to n - 1; step i takes durationsi minutes. A pair u, v in dependencies means step u must finish before step v starts. Any number of steps…

  Last asked Oct 2026Were you asked this too?
• 

  Fewest moves for a chess piece to capture the kingCodingA rectangular board has blocked squares, your piece and the opposing king. Your piece's type decides the directions it may step in, and it can never move onto a blocked square…

  Last asked Oct 2026Were you asked this too?
• 

  Evaluate divisionCodingYou get equations a / b = value between string variables, each standing for a positive real number, and a large batch of queries c / d. Answer every query from the equations, or…

  Last asked Sep 2026Were you asked this too?
• 

  Coordinate a fleet of restaurant robotsSystem designDesign the system that coordinates many robots working in a restaurant. Start by pinning down what work the robots do, then cover how tasks are assigned, how execution state is…

  Last asked Sep 2026Were you asked this too?
• 

  Design a Kafka-based file watcher for millions of filesSystem designDesign a file watcher that tracks millions of files and publishes change events to downstream consumers through Kafka. Cover the first full discovery of files, ongoing changes…

  Last asked Sep 2026Were you asked this too?
• 

  Grid reachability for a robot that cannot reverseCodingA robot moves on a grid of open cells, blocked cells, a start S and a destination D. It always faces one of four directions, can never turn around, and may only turn in the ways…

  Last asked Sep 2026Were you asked this too?
• 

  Ones and zeroesCodingGiven a list of binary strings and two budgets, at most maxzeros zeros and at most maxones ones in total, choose as many strings as possible so that the chosen strings together…

  Last asked Sep 2026Were you asked this too?
• 

  Predict click-through rate for music recommendationsML designDesign a model that predicts whether a user will click a recommended song. Explain how you would embed songs, how you handle the different kinds of features, and how you would…

  Last asked Sep 2026Were you asked this too?
• 

  Design a notification systemSystem designA shared service other teams call to send push, email and SMS notifications: templates, user preferences, retries, deduplication and rate limits.

  Last asked Sep 2026Were you asked this too?
• 

  Temporal key-value store with point-in-time reads and restoreCodingBuild an in-memory key-value store that keeps every version of every key, so you can ask what a key held at any point in time. Implement the TemporalKVStore class: -…

  Last asked Sep 2026Were you asked this too?
• 

  Valid palindrome ignoring case and punctuationCodingDecide whether a string reads the same forwards and backwards when you ignore letter case and every character that is not a letter or a digit.

  Last asked Aug 2026Were you asked this too?
• 

  Earliest pair with a target sumCodingGiven an array of numbers and a target, find the pair of elements that sums to the target and appears earliest in the array.

  Last asked Aug 2026Were you asked this too?
• 

  Valid parenthesesCodingGiven a string of brackets (), and {}, decide whether every bracket is closed by the matching type in the right order.

  Last asked Aug 2026Were you asked this too?
• 

  Count customers who visited on more than one dateCodingGiven visit records of a customer and a date, count the customers who visited on at least two different dates.

  Last asked Aug 2026Were you asked this too?
• 

  Angle between clock handsCodingGiven a time in hours and minutes, return the smaller angle between the hour hand and the minute hand.

  Last asked Aug 2026Were you asked this too?
• 

  Roofline analysis of a BF16 MLP layerML designApply roofline analysis to an MLP layer running in BF16: count its floating-point operations and the bytes it moves, compute its arithmetic intensity, and decide whether it is…

  Last asked Aug 2026Were you asked this too?
• 

  Lowest common ancestor of a binary treeCodingGiven a binary tree (no ordering on the values) and two of its nodes, return their lowest common ancestor: the deepest node that has both in its subtree.

  Last asked Aug 2026Were you asked this too?
• 

  Rearrange digits so no neighbours sum above nineCodingRearrange a list of digits so that no two adjacent digits sum to more than nine, or report that it cannot be done.

  Last asked Jul 2026Were you asked this too?
• 

  Predict a future point with a fitted lineML designFit a straight line to a set of data points and use it to predict the value at a future point. Explain how the fit is computed and how far you would trust the prediction.

  Last asked Jul 2026Were you asked this too?
• 

  BIOS and UEFI firmwareCodingExplain what BIOS and UEFI firmware do when a machine boots and how they differ, including how each finds and starts the operating system.

  Last asked Jul 2026Were you asked this too?
• 

  Edit distanceCodingReturn the fewest single-character insertions, deletions and replacements that turn one string into another.

  Last asked Jul 2026Were you asked this too?
• 

  Concurrent restaurant waitlist and seatingOO designDesign and code a restaurant's waitlist and seating: parties join the list, tables free up, and parties get seated. Keep it correct when many requests happen at the same time.

  Last asked Jul 2026Were you asked this too?
• 

  Range moduleCodingTrack half-open integer ranges left, right): add a range, remove a range, and ask whether every number in a range is currently tracked.

  Last asked Jul 2026Were you asked this too?
• 

  Best time to buy and sell stock, every variantCodingGiven daily stock prices, solve the variants of the maximum-profit problem (for example a single trade, many trades, or at most k trades) with one unified approach.

  Last asked Jul 2026Were you asked this too?
• 

  Design Amazon LockerSystem designLet customers pick a locker location at checkout, assign a compartment that fits the package, and give them a code to collect it within a few days.

  Last asked Jul 2026Were you asked this too?
• 

  Regular expression matchingCodingDecide whether a whole string matches a pattern where . matches any single character and matches zero or more of the element before it.

  Last asked Jul 2026Were you asked this too?
• 

  Design a news feedSystem designDesign the home feed for a social network with 1B users: posts from people you follow, ranked, fresh within seconds.

  Last asked Jun 2026Were you asked this too?
• 

  Single element in a sorted arrayCodingIn a sorted array where every value appears exactly twice except one, find the value that appears once, in logarithmic time.

  Last asked Jun 2026Were you asked this too?
• 

  GRPO deep dive for a reasoning LLMML designExplain GRPO and why it can drop the critic that PPO uses. Then discuss the parallelism used to train a reasoning language model, multi-head latent attention (MLA), and how you…

  Last asked Jun 2026Were you asked this too?
• 

  Detect and break a cycle in a linked listCodingDecide whether a singly linked list has a cycle, find the node where the cycle begins, and break the cycle so the list ends.

  Last asked Jun 2026Were you asked this too?
• 

  Fewest bills and coins to make changeCodingGiven an amount and the denominations of the bills and coins available, return the fewest pieces that add up to the amount.

  Last asked Jun 2026Were you asked this too?
• 

  Team with the highest average salary in an org chartCodingGiven an org chart where every employee has a salary, find the manager whose team (the manager and everyone below them) has the highest average salary.

  Last asked Jun 2026Were you asked this too?
• 

  Design a perishable-goods inventory and location trackerSystem designDesign a system that tracks perishable goods: what is in stock, where each item is, and when it expires.

  Last asked Jun 2026Were you asked this too?
• 

  Asteroid collisionCodingAsteroids move along a line; each has a size and a direction. When two meet, the smaller one explodes, and both explode if they are the same size. Return the asteroids left after…

  Last asked Jun 2026Were you asked this too?
• 

  Design an advertiser metrics tracking platformSystem designDesign a platform that tracks performance metrics for advertisers and lets them see how their campaigns are doing.

  Last asked May 2026Were you asked this too?
• 

  Filter events and route them to queuesCodingProcess a stream of events: apply filter rules to each one and route every event that passes to the right queue.

  Last asked May 2026Were you asked this too?
• 

  Design a logging serviceSystem designIngest logs from every service at terabytes per day, make them searchable within seconds, and keep them cheaply for months.

  Last asked May 2026Were you asked this too?
• 

  Design human avoidance for warehouse robotsSystem designDesign how robots in a warehouse detect and avoid the people working on the same floor: sensing, what each robot decides on its own versus what a central system decides, and…

  Last asked May 2026Were you asked this too?
• 

  Unique pairs with a target sumCodingReturn each distinct pair of values from an array that sums to a target, counting a pair only once even when the values repeat.

  Last asked May 2026Were you asked this too?
• 

  Extensible cinema ticket pricing engineOO designDesign a ticket pricing engine for a cinema, built so that new pricing rules can be added later without rewriting the engine.

  Last asked May 2026Were you asked this too?
• 

  Fewest points to pay across reward programsCodingA user holds points in several programs (airline miles, credit card points, store points). Each program has a balance and a dollar value per point that changes daily. To pay a…

  Last asked May 2026Were you asked this too?
• 

  Set over a bounded range of integersCodingImplement a set of integers drawn from a known bounded range, with add, remove and contains.

  Last asked Apr 2026Were you asked this too?
• 

  Validate a binary search treeCodingDecide whether a binary tree is a valid binary search tree.

  Last asked Apr 2026Were you asked this too?
• 

  Every ordering of N students in a line, then in a circleCodingPrint every way N students can stand in a line. Follow-up: they stand in a circle instead, where rotations of the same arrangement count once.

  Last asked Apr 2026Were you asked this too?
• 

  Longest sequence whose neighbours differ by less than kCodingA variant of longest consecutive sequence: from the values in an array, find the longest sequence in which each neighbouring pair differs by less than k.

  Last asked Apr 2026Were you asked this too?
• 

  Siblings, cousins or neither: two nodes in a treeCodingGiven a tree and two of its nodes, say whether they are siblings (same parent), cousins (same depth, different parents) or neither.

  Last asked Apr 2026Were you asked this too?
• 

  Kth largest element in two sorted arraysCodingFind the kth largest element across two sorted arrays without merging them. Reported on 1point3acres' Glean bank; reconstructed in our own words.

  Last asked Mar 2026Were you asked this too?
• 

  Breadth-first web crawler with retriesCodingIn your own IDE, write a crawler that walks a given website breadth-first from a start URL, normalizing URLs and retrying requests that fail. API docs are allowed; AI tools are…

  Last asked Mar 2026Were you asked this too?
• 

  Build a binary tree from parent-child descriptionsCodingEach description gives a parent value, a child value, and whether the child is the left or right child. Build the binary tree and return its root.

  Last asked Mar 2026Were you asked this too?
• 

  Tell me about a time you traded short-term gain for long-term successBehavioralDescribe a time you gave up a short-term benefit, such as a faster launch or an easy win, for a better long-term outcome. Explain the choice, how you convinced others, and how it…

  Last asked Mar 2026Were you asked this too?
• 

  Message latency from send and receive logsCodingTwo CSV files describe messages between two machines: one lists when machine A sent each message, the other when machine B received it. Match the rows by message and compute each…

  Last asked Mar 2026Were you asked this too?
• 

  Unique Morse code wordsCodingTranslate each word into Morse code by joining the codes of its letters, and return how many different translations there are.

  Last asked Feb 2026Were you asked this too?
• 

  Merge two sorted arrays in placeCodingTwo integer arrays, arr1 and arr2, are each sorted in ascending order. Merge arr2 into arr1 without using another array, so that arr1 ends up holding all the values, still…

  Last asked Feb 2026Were you asked this too?
• 

  Database internals: WAL, MVCC, replication and recoveryCodingExplain the internals a relational database relies on: write-ahead logging and why it makes commits durable, multi-version concurrency control and how readers avoid blocking…

  Last asked Jan 2026Were you asked this too?
• 

  Design a cloud database's write path and crash recoverySystem designDesign how writes flow through a managed cloud relational database: from a client's commit to durable storage, how the data is replicated across machines or zones, and how the…

  Last asked Jan 2026Were you asked this too?
• 

  Find when failures started in a logCodingA service writes a time-ordered log of request results, and at some point it started failing. Find the moment the failures began. Discuss the approach when you can only read the…

  Last asked Jan 2026Were you asked this too?
• 

  Inheritance, polymorphism, constructors and destructorsCodingExplain the difference between inheritance and polymorphism, then write a short example in which a child class overrides a method of its parent. Next, compare constructors and…

  Last asked Jan 2026Were you asked this too?
• 

  Print the odd numbers in a listCodingGiven a list of integers, print every odd number in it, in order. Mind negative numbers and an empty list.

  Last asked Jan 2026Were you asked this too?
• 

  Responsive grid of fixed-size boxesCodingBuild a web page that lays out fixed-size boxes in a grid that reflows as the window gets wider or narrower: as many boxes per row as fit, wrapping to new rows. Explain the CSS…

  Last asked Jan 2026Were you asked this too?
• 

  Serialize and deserialize a binary treeCodingTurn a binary tree into a string and rebuild the identical tree from that string. Choose a format (pre-order with null markers, or level order), handle empty trees and negative…

  Last asked Jan 2026Were you asked this too?
• 

  Word break II: every way to split a sentenceCodingGiven a string and a dictionary of words, return every sentence you can form by splitting the string into dictionary words, with words separated by spaces. Words may be reused…

  Last asked Jan 2026Were you asked this too?
• 

  Robot charging controller with exclusive stationsCodingA fleet of robots shares a small number of charging stations. A robot whose battery drops below 50% should go to a free station, and a robot charging above 95% may leave and go…

  Last asked Jan 2026Were you asked this too?
• 

  Fewest emergency restocks to keep inventory validCodingYour stock changes every day by taski (positive or negative). On days where taski == 0 the stock is checked and must not be negative, and at no time may the stock exceed…

  Last asked Jan 2026Were you asked this too?
• 

  Score an array by taking the smallest and marking its neighboursCodingStart with every element of an array unmarked and a score of 0. Repeatedly pick the smallest unmarked value (the leftmost one on a tie), add it to the score, and mark it together…

  Last asked Jan 2026Were you asked this too?
• 

  Design a real-time temperature monitoring systemSystem designCollect readings from millions of sensors every few seconds, show live and historical temperatures, and alert when a sensor goes out of range or silent.

  Last asked Jan 2026Were you asked this too?
• 

  Weighted random value generatorCodingGiven values with positive weights, write a generator that returns a value at random with probability proportional to its weight. Build it once and answer many calls quickly, and…

  Last asked Jan 2026Were you asked this too?
• 

  Design a package installer with dependenciesSystem designDesign a package installer: a user asks for a package and the installer fetches it together with everything it depends on, in a valid order. Cover how dependencies and versions…

  Last asked Jan 2026Were you asked this too?
• 

  Top k lottery winners by spendingCodingGiven lottery entries that record who bought tickets and how much they spent, return the top k people ranked by total spending. Discuss ties and how you would keep the answer…

  Last asked Jan 2026Were you asked this too?
• 

  Linear regression with hand-written gradient descentCodingFit a one-feature linear regression by gradient descent on mean squared error, without an ML library. Then discuss choosing the learning rate, when to stop, and how to spot a…

  Last asked Dec 2025Were you asked this too?
• 

  Word ladderCodingGiven a start word, an end word and a word list, find the length of the shortest sequence from start to end in which each step changes exactly one letter and every word after the…

  Last asked Dec 2025Were you asked this too?
• 

  Parking lot occupancy peaks from entry and exit eventsCodingYou get parking events carid, time, 'entry' 'exit', not necessarily in order. 1. What is the largest number of cars that were in the lot at the same time? 2. Return the time…

  Last asked Dec 2025Were you asked this too?
• 

  Design a hash map without built-in librariesCodingImplement a hash map with put, get and remove without using any built-in hash table. Choose the bucket layout, the hash function and how collisions are handled, and explain when…

  Last asked Nov 2025Were you asked this too?
• 

  Design a basic credit card systemOO designDesign the classes for a simple credit card system: cards and accounts, a credit limit, purchases, payments and the balance. Show how a purchase is authorized against the limit…

  Last asked Oct 2025Were you asked this too?
• 

  Look up a value in a nested object by pathCodingGiven a nested object (maps and lists inside each other) and a path string such as a.b.0.c, return the value at that path, or a default when any step is missing. Handle list…

  Last asked Oct 2025Were you asked this too?
• 

  Maximum sum of non-adjacent houses, on a line, a circle and a treeCodingEach house holds some value and you cannot take two neighbours. Find the best total for houses in a row, then for houses arranged in a circle, then for houses arranged as a binary…

  Last asked Oct 2025Were you asked this too?
• 

  Cells water reaches flowing downhillCodingA 2D map gives the height of each cell. A drop of water lands on one cell and flows to neighbouring cells (up, down, left, right) whose height is not greater than the cell it is…

  Last asked Oct 2025Were you asked this too?
• 

  Debounce and throttle in JavaScriptCodingImplement debounce(fn, wait) and throttle(fn, wait) in JavaScript. Keep this and the arguments of the latest call, support cancelling, and discuss options to fire on the leading…

  Possibly retiredWere you asked this too?
• 

  Design a basic task management systemSystem designDesign a simple task management system: users create tasks, assign them, set due dates and statuses, and see their lists. Cover the API, the data model, notifications for due…

  Possibly retiredWere you asked this too?
• 

  Design a RAG system end to endAI systemDesign a retrieval-augmented generation system from documents to answers: ingesting and chunking documents, embeddings and the index, retrieval and reranking, the prompt to the…

  Possibly retiredWere you asked this too?
• 

  Design a top-K popular items systemSystem designReport the K most viewed or played items over sliding windows (last minute, hour, day) from a firehose of billions of events per day.

  Possibly retiredWere you asked this too?
• 

  Design a traffic light control systemOO designModel an intersection's traffic lights with phases and timings, pedestrian requests and an emergency override, as a clear state machine.

  Possibly retiredWere you asked this too?
• 

  Design an e-commerce recommendation systemML designDesign the system that recommends products to shoppers on an e-commerce site. Cover candidate generation, ranking features and model, training data from views and purchases, cold…

  Possibly retiredWere you asked this too?
• 

  Diameter of a binary treeCodingReturn the number of edges on the longest path between any two nodes of a binary tree. The path need not pass through the root. Solve it in one pass.

  Possibly retiredWere you asked this too?
• 

  Extensible event ticketing systemOO designWrite an EventTicketSystem that sells tickets for different kinds of events, such as concerts, movies and sports games. Adding a new kind of event later should not require…

  Possibly retiredWere you asked this too?
• 

  Filter and analyze logs with an object-oriented designOO designDesign classes that read a stream of log entries, some of them errors, filter them by rules such as level, time range or source, and report simple analytics such as error counts…

  Possibly retiredWere you asked this too?
• 

  Keyboard and mouse input systemOO designDesign classes for an input system that records what a user does with the keyboard and the mouse (key presses, clicks, movement) so that the program can tell what was input…

  Possibly retiredWere you asked this too?
• 

  Lower and upper bound binary searchCodingGiven an array sorted in non-decreasing order and a target, return the first index whose value is at least the target and the first index whose value is greater than the target…

  Possibly retiredWere you asked this too?
• 

  Search a sorted array of unknown lengthCodingA sorted array can only be read through get(i), which signals when i is past the end; you do not know the length. Return the index of a target value or -1. Find a range that…

  Possibly retiredWere you asked this too?
• 

  Shortest unsorted continuous subarrayCodingFind the shortest contiguous subarray that, if sorted, makes the whole array sorted, and return its length. Start from sorting a copy, then find an O(n) two-pointer solution.

  Possibly retiredWere you asked this too?
• 

  Design a payment fraud detection systemML designScore every card payment for fraud within tens of milliseconds, balancing blocked fraud against declined good customers, with labels that arrive weeks later.

  Possibly retiredWere you asked this too?
• 

  Design an email spam detection systemML designDesign a system that flags spam email before it reaches the inbox. Cover the features (content, sender, links, behavior), the model, labels from user reports, adversaries who…

  Possibly retiredWere you asked this too?
• 

  Lock, unlock and upgrade nodes in a treeCodingA tree is given by a parent array. Implement lock(node, user), unlock(node, user) and upgrade(node, user): a node can be locked by a user if it is unlocked; unlocked only by the…

  Possibly retiredWere you asked this too?
• 

  Most tasks finished before their deadlinesCodingGiven tasks with durations and deadlines, run them one at a time and choose as many as possible so that each finishes by its deadline. Return how many. Sort by deadline and use a…

  Possibly retiredWere you asked this too?
• 

  Place items into the earliest bin that fitsCodingBins have capacities and items arrive in order. Put each item into the first bin, from left to right, that still has room for it. Return where each item goes. Do better than…

  Possibly retiredWere you asked this too?
• 

  Time-series manipulation with pandas groupbyCodingGiven a pandas DataFrame of timestamped records, answer questions with groupby: aggregate per group and time period, resample, and compute rolling or cumulative values. Explain…

  Possibly retiredWere you asked this too?
• 

  Substring with concatenation of all wordsCodingGiven a string and a list of words of equal length, return every start index where a substring is some concatenation of all the words, each used exactly once. Use a sliding window…

  Possibly retiredWere you asked this too?
• 

  Cheapest way to make product sizes distinctCodingProducts have sizes sizei, and raising product i's size by one costs costi. Sizes may only grow. Return the least total cost to make all sizes distinct. The same screen also had a…

  Possibly retiredWere you asked this too?
• 

  Count of smaller numbers after selfCodingFor every element of an integer array, count how many elements to its right are smaller, and return those counts. The O(n^2) scan is too slow; use merge sort that tracks original…

  Possibly retiredWere you asked this too?
• 

  Design a parking lotOO designModel a multi-floor parking lot with spot types for motorcycles, cars and trucks: park, unpark, find free spots, and charge by time.

  Possibly retiredWere you asked this too?
• 

  Fewest intervals to remove so one covers the restCodingGiven a list of intervals, remove as few as possible so that among the remaining intervals at least one covers all the others. Return how many you remove.

  Possibly retiredWere you asked this too?
• 

  First unique character in a stringCodingReturn the index of the first character in a string that appears only once, or -1 if every character repeats. Do it in two passes with a count table.

  Possibly retiredWere you asked this too?
• 

  Make sure every cluster job completesSystem designA company runs many jobs on a high-performance cluster and needs a service that makes sure every one of them completes. You get two functions (for example, one that starts a job…

  Possibly retiredWere you asked this too?
• 

  Design pickup point planning for ride-hailingSystem designDesign how a ride-hailing app suggests where a rider should be picked up: candidate points near the rider, ranking them by walking distance, road access, and driver arrival time…

  Possibly retiredWere you asked this too?