Coinbase frontend engineer interviews emphasise JavaScript, DOM manipulation, CSS, accessibility, browser APIs, and UI component architecture.
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coding
Medium
Verified Question
#1
1. Generate NFT
Category: String coding problem
Question You are designing an NFT generation engine. You are given a set of Traits, where each trait has a name and a list of possible...
Input: ListOutput: Array
coding
Medium
Verified Question
#2
2. Blockchain Mining
Category: Dynamic programming coding problem
Question You are building a block construction module for a blockchain node. The goal is to select a subset of pending transactions to include in...
Input: Graph (nodes and edges)Output: Computed result
coding
Medium
Verified Question
#3
3. Crypto Trading System Stream
Category: String coding problem
Question Design a crypto trading system that manages a stream of orders. The system should support various operations like placing, pausing,...
Input: Array of stringsOutput: Computed result
coding
Hard
Verified Question
#4
4. Design Iterators
Category: Array coding problem
Question For this problem, you will be designing a series of different iterator classes. This problem is split into multiple related parts that...
Input: Array of integersOutput: Computed result
coding
Medium
Verified Question
#5
5. Food Delivery System
Category: Trie-based coding problem
Question For this problem, you will be designing a food delivery system. This problem is split into three related parts, evolving from basic data...
Input: ListOutput: Computed result
coding
Hard
Verified Question
#6
6. Transaction System
Category: Tree coding problemFor this problem, you will be designing a system to handle financial transactions and account balances. This problem is split into three related...Input: List
Output: Integer
coding
Hard
Verified Question
#7
7. OA[CodeSignal] Cloud File Storage System
Category: Graph coding problem
Question Your task is to implement a simple in-memory cloud storage system that maps objects (files) to their metadata (name, size, etc.). You...
Input: Graph (nodes and edges)Output: Array
coding
Hard
Verified Question
#8
8. OA[CodeSignal] Design Banking System
Category: Graph coding problem
Question Design a banking system that supports account management, transactions, and various financial operations.
Input: Graph (nodes and edges)Output: Computed result
coding
Hard
Verified Question
#9
9. Capital Gains Tax Calculator
Category: String coding problemYou are given a chronologically sorted list of stock transactions. Each transaction is a list of strings in the format `[<timestamp>, <type>,...Input: Array of strings
Output: Computed result
coding
Medium
Verified Question
#10
10. Service Log Aggregator
Category: Trie-based coding problemA distributed system emits log entries from multiple services and worker threads. Each log entry is a colon-separated string in the format...Input: Array
Output: Computed result
coding
Hard
Verified Question
#11
11. OA [CodeSignal] Knowledge Base System
Category: Graph coding problemDesign and implement a personal knowledge base called
KnowledgeBaseSystem that stores articles with CRUD operations. The system operates entirely...Input: Graph (nodes and edges)Output: Computed result
coding
Medium
Verified Question
#12
12. OA [CodeSignal] Workspace Tracker
Category: Interval-based coding problemBuild a system to track desk workers at a shared office space. The system records when each worker enters and leaves and computes how long they have...Input: String
Output: Array
coding
Hard
Verified Question
#13
13. Transaction Query Engine
Category: String coding problemDesign a system to filter and paginate a list of transaction records. Each record is a list of strings in the format `[timestamp, id, userId,...Input: Array of strings
Output: Computed result
coding
Medium
Verified Question
#14
14. Exchange Rate Finder
Category: String coding problemYou are given a set of currency exchange relationships. Each relationship specifies a direct exchange rate between two currencies. Rates are...Input: List
Output: Computed result
coding
Hard
Verified Question
#15
15. Order Matching Engine
Category: String coding problemYou are managing a cryptocurrency order book. The book holds buy and sell orders placed by traders. - A buy order indicates the maximum price a...Input: String
Output: Computed result
coding
Hard
Verified Question
#16
16. Account Transfer System
Category: String coding problemYou are given a list of fund transfer instructions and a set of accounts with initial balances. Each transfer moves a fixed percentage of the...Input: List
Output: Computed result
coding
Hard
Verified Question
#17
17. Restaurant Delivery Network
Category: String coding problemYou are building a food discovery platform. Given a user's location, a list of restaurants with their coordinates, and a menu of items with prices,...Input: List
Output: Computed result
coding
Medium
closure
#1
1. [OA] Closures — Create a series of functions to track user account balance on Coinbase.
As a finance platform, accurately maintaining user balances is fundamental. Understanding closures helps in creating a secure balance management system.
Problem Statement: You need to define a function
Example 1:
Input:
Output:
Explanation: The initial balance was 100, and after depositing 50, it became 150.Example 2:
Input:
Output:
Explanation: After withdrawing 30, the balance updates to 120.Constraints:
Problem Statement: You need to define a function
createAccountManager(initialBalance: number): { deposit: Function; withdraw: Function; getBalance: Function; } that returns an object with methods to deposit, withdraw, and getBalance. Using closures, ensure that the balance is encapsulated and not directly accessible.deposit(amount: number): void— Adds an amount to the balance.withdraw(amount: number): void— Reduces the balance by the specified amount if sufficient funds are available.getBalance(): number— Returns the current balance.
Example 1:
Input:
const account = createAccountManager(100); account.deposit(50); account.getBalance();Output:
150Explanation: The initial balance was 100, and after depositing 50, it became 150.Example 2:
Input:
account.withdraw(30); account.getBalance();Output:
120Explanation: After withdrawing 30, the balance updates to 120.Constraints:
- The
initialBalanceis a non-negative integer. - Withdrawals cannot exceed the current balance.
coding
Hard
concurrency
#2
2. [OA] Event Loop — Implement a JavaScript function to simulate the behavior of Coinbase’s frontend event loop.
In the context of synchronous and asynchronous operations, understanding how the event loop handles tasks is crucial for performance in high-frequency trading platforms like Coinbase.
Problem Statement: You need to implement a function
Example 1:
Input:
Output:
Explanation: The first promise is resolved immediately, then the second waits for 100ms before executing, followed by the final promise.Example 2:
Input:
Output:
Problem Statement: You need to implement a function
simulateEventLoop(tasks: Array<Promise<void>>): void that takes an array of promises representing asynchronous tasks and executes them in a way that reflects the behavior of the event loop. Ensure that any tasks scheduled in the event loop (using setTimeout or similar) are executed only after the current stack is clear.simulateEventLoop(tasks: Array<Promise<void>>): void— Simulates the event loop and executes tasks in order.
Example 1:
Input:
simulateEventLoop([Promise.resolve(), new Promise((res) => setTimeout(res, 100)), Promise.resolve()])Output:
Executed (in order: resolve, wait, resolve)Explanation: The first promise is resolved immediately, then the second waits for 100ms before executing, followed by the final promise.Example 2:
Input:
simulateEventLoop([new Promise((res) => setTimeout(res, 50)), Promise.resolve(), new Promise((res) => setTimeout(res, 20))])Output:
Executed (in order: wait 50ms, resolve, wait 20ms)Constraints:1 <= tasks.length <= 10^4- Each task will either be a resolved promise or a promise that resolves after a timeout.
system design
Senior
api design
#3
3. [OA] Client-side Router — Design a basic client-side router for the Coinbase web application.
With the dynamic nature of financial applications, a smooth client-side routing experience is integral for user retention on Coinbase.
Problem Statement: You need to implement a class
Example 1:
Input:
Output:
Explanation: After navigating to
Input:
Output:
Problem Statement: You need to implement a class
ClientRouter that manages different routes in a single-page application. Users will navigate between different components based on the URL without refreshing the page.addRoute(path: string, component: Function): void— Adds a new route along with its corresponding component.navigate(path: string): void— Navigates to the given path and renders the associated component.getCurrentPath(): string— Returns the current path the user is on.
Example 1:
Input:
const router = new ClientRouter(); router.addRoute('/home', HomeComponent); router.navigate('/home');Output:
Rendered HomeComponentExplanation: After navigating to
/home, the associated component is rendered.Example 2:Input:
router.addRoute('/about', AboutComponent); router.navigate('/about');Output:
Rendered AboutComponentConstraints:- All paths are unique and in the format of a valid URL path.
system design
Senior
api design
#4
4. [OA] Virtual DOM — Design a lightweight Virtual DOM to improve rendering performance on Coinbase’s web interface.
Given the dynamic nature of cryptocurrency data, efficiently updating the UI is essential in the Coinbase platform. A Virtual DOM can help minimize direct manipulation of the actual DOM.
Problem Statement: You need to implement a class
Example 1:
Input:
Output:
Input:
Output:
Problem Statement: You need to implement a class
VirtualDOM that can create, update, and render a lightweight representation of a real DOM. This is vital to reduce expensive layout recalculations and improve responsiveness.createElement(tag: string, props: Object, children: Array<VirtualNode>): VirtualNode— Create a new Virtual Node.update(oldNode: VirtualNode, newNode: VirtualNode): VirtualNode— Update an old node to match a new one and return the updated Virtual Node.render(node: VirtualNode): HTMLElement— Convert a Virtual Node back into a real DOM HTMLElement.
Example 1:
Input:
const vNode = virtualDOM.createElement('div', { className: 'container' }, []);Output:
Virtual Node createdExample 2:Input:
virtualDOM.update(oldVNode, newVNode);Output:
Updated Virtual NodeConstraints:- The tag name contains only alphabetic characters.
- Props is a simple object and children are always an array of Virtual Nodes.
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