CodeSignal Technical Assessment Domain-Specific Knowledges 3

Question 1

What is the primary advantage of using an index on a database column?

Accepted Answer

Speeds up SELECT queries at the cost of slower writes

Answer

Reduces disk storage for the table

Answer

Enforces uniqueness by default

Answer

Automatically partitions the table for parallel queries

Question 2

In JavaScript, what does the event loop's 'microtask queue' hold, and when does it drain?

Accepted Answer

Promise callbacks (.then/.catch); after the current task completes, before the next macrotask

Answer

setTimeout callbacks; after each macrotask

Answer

DOM event listeners; at the start of each frame

Answer

WebWorker messages; continuously in a background thread

Question 3

Which TCP mechanism prevents a fast sender from overwhelming a slow receiver?

Accepted Answer

Flow control via the receive window

Answer

Nagle's algorithm

Answer

Congestion control via CWND

Answer

SYN cookies

Question 4

In Python, what is the time complexity of checking whether an element exists in a set?

Accepted Answer

O(1) average

Answer

O(n)

Answer

O(log n)

Answer

O(n log n)

Question 5

Which design pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable at runtime?

Accepted Answer

Strategy

Answer

Observer

Answer

Template Method

Answer

Chain of Responsibility

Question 6

What is 'eventual consistency' in distributed systems?

Accepted Answer

Given no new writes, all replicas will converge to the same value over time

Answer

All nodes see every write within a fixed time bound

Answer

A transaction is committed only after a quorum of nodes agrees

Answer

Reads always return the most recent committed write

Question 7

In React, what triggers a component to re-render?

Accepted Answer

Changes to state or props, or a parent re-render

Answer

Any variable assignment inside the component function

Answer

DOM mutations triggered by the browser

Answer

Only explicit calls to ReactDOM.render()