Canonical Solutions

Master Tech Interviews with Expert-Curated Solutions.

Deep dives into canonical solutions, architectural patterns, and the rubrics Big Tech uses to identify top talent. Master System Design, Frontend Architecture, Coding, and Behavioral interviews with our engineering blueprints.

Coding

Mar 4, 2026

String Transformation via Character Mapping

abstract

Given two strings str1 and str2 of equal length consisting of lowercase English letters, determine if str1 can be transformed into str2. A transformation consists of replacing all occurrences of a specific character with another lowercase letter. You may perform any number of such transformations sequentially. Note that a transformation must apply to all instances of the chosen character simultaneously.

Photo & Video Sharing Social Network

abstract

Design a photo and video sharing social network similar to Instagram. The system should support media uploads with processing and CDN delivery, algorithmic feeds, stories with 24-hour expiry, direct messaging, and engagement features for hundreds of millions of daily active users.

Local Business Discovery Platform

abstract

Design a local business discovery and review platform similar to Yelp. The system should support geo-based business search, structured business listings, user-submitted reviews and ratings, photo uploads, and personalized recommendations for millions of users across cities worldwide.

Reverse a Singly Linked List

abstract

Given the head of a singly linked list, implement a function to reverse the list in-place and return the new head pointer. Discuss the trade-offs between an iterative approach and a recursive approach, specifically focusing on time and space complexity constraints.

Climbing Stairs Path Counting

abstract

You are climbing a staircase that takes n steps to reach the top. Each time you can either take 1 or 2 steps. Implement an optimal function in C++ to determine the total number of distinct ways you can reach the top, considering constraints where n can be up to 45 and efficiency in both time and space is required.

Real-time Collaborative Whiteboard Architecture

abstract

Design a frontend architecture for a high-performance, real-time collaborative whiteboard. The system must handle low-latency vector graphics synchronization, conflict resolution for concurrent multi-user editing, and efficient network utilization for mobile-friendly bandwidth consumption.

RequestAnimationFrame

View

SQL

Apr 10, 2026

Identifying Multi-Year Customer Loyalty

abstract

Given a table of tax filing records, identify all users who have used the 'TurboTax' product line to file their taxes for at least three consecutive calendar years. Ensure your solution accounts for users who may have multiple filing entries within the same year and returns a unique list of user IDs in ascending order.

Real-time Collaborative Code Editor Design

abstract

Design a collaborative web-based IDE frontend. The system must support real-time multi-user editing, conflict-free synchronization, syntax highlighting for multiple languages, and a robust offline-first experience that merges changes automatically when the user reconnects.

Delivering Complex Projects Under Ambiguity

abstract

Describe a situation where you led a high-stakes technical project despite having significant gaps in the initial requirements. How did you structure the project to handle the 'known unknowns,' and how did you manage stakeholder expectations to ensure a successful delivery?

Senior Level

ambiguity

stakeholder management

Sum of Sortable Partition Sizes

abstract

Given an integer array `nums` of length `n`, a positive integer `k` is defined as 'sortable' if `k` is a divisor of `n` and the array can be sorted into non-decreasing order by partitioning it into consecutive subarrays of length `k` and independently rotating each subarray any number of times. Write a function to return the sum of all such sortable integers `k`. Your solution should handle large inputs efficiently and account for duplicate elements.

Robot Room Cleaner

abstract

Given a robot in an unknown grid that can move, turn, and clean, design an algorithm using only the robot's API to clean all reachable empty cells.

Social Media Microblogging Platform

abstract

Design a social media platform similar to Twitter. The system should support posting short messages, following other users, delivering personalized real-time feeds, handling viral content fan-out, and serving hundreds of millions of daily active users at low latency.

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Master Tech Interviews with Expert-Curated Solutions.

String Transformation via Character Mapping

Photo & Video Sharing Social Network

Local Business Discovery Platform

Reverse a Singly Linked List

Climbing Stairs Path Counting

Real-time Collaborative Whiteboard Architecture

Identifying Multi-Year Customer Loyalty

Real-time Collaborative Code Editor Design

Delivering Complex Projects Under Ambiguity

Sum of Sortable Partition Sizes

Robot Room Cleaner

Social Media Microblogging Platform

The Golden Solutions for Real Interviews.

Mastery Checklist

System Design & Distributed Architecture

Coding Patterns & Algorithmic Strategy

Behavioral Strategy & Leadership Principles

ML System Design & AI Architecture

SQL Optimization & Data Modeling

Frontend Architecture & UI Systems

Master Tech Interviews with Expert-Curated Solutions.

The Golden Solutions for Real Interviews.

Mastery Checklist

System Design & Distributed Architecture

Coding Patterns & Algorithmic Strategy

Behavioral Strategy & Leadership Principles

ML System Design & AI Architecture

SQL Optimization & Data Modeling

Frontend Architecture & UI Systems

Master Tech Interviews with Expert-Curated Solutions.

String Transformation via Character Mapping

Photo & Video Sharing Social Network

Local Business Discovery Platform

Reverse a Singly Linked List

Climbing Stairs Path Counting

Real-time Collaborative Whiteboard Architecture

Identifying Multi-Year Customer Loyalty

Real-time Collaborative Code Editor Design

Delivering Complex Projects Under Ambiguity

Sum of Sortable Partition Sizes

Robot Room Cleaner

Social Media Microblogging Platform

The Golden Solutions for Real Interviews.

Mastery Checklist

System Design & Distributed Architecture

Coding Patterns & Algorithmic Strategy

Behavioral Strategy & Leadership Principles

ML System Design & AI Architecture

SQL Optimization & Data Modeling

Frontend Architecture & UI Systems