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

Indexes create auxiliary data structures that accelerate reads but must be maintained on every insert, update, or delete.

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

Microtasks (Promise continuations, queueMicrotask) drain completely after each macrotask and before the next macrotask begins.

Question 3

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

Accepted Answer

Flow control via the receive window

Answer

TCP flow control uses the receiver-advertised window size (rwnd) to limit how much data the sender can have in-flight at once.

Question 4

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

Accepted Answer

O(1) average

Answer

Python sets are implemented as hash tables, so membership tests are O(1) on average, O(n) in the degenerate collision case.

Question 5

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

Accepted Answer

Strategy

Answer

The Strategy pattern lets you select an algorithm at runtime by programming to an interface rather than a concrete class.

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