Senior Evaluator Terms

Question 1

(Performance & Architecture)

Request Waterfall

Answer 1

A “Request Waterfall” is when nested components wait for their parents’ data fetching to finish before starting their own (which is bad).

Question 2

(Performance & Architecture)

Progressive Enhancement

Answer 2

Ensuring the app works (even partially) before the JavaScript has finished loading. (Good)

Question 3

(Performance & Architecture)

Referential Identity

Answer 3

Whether a function or object is the exact same instance in memory between renders (crucial for useMemo / useCallback).

Question 4

(Performance & Architecture)

Hydration Mismatch

Answer 4

When the server-rendered HTML doesn’t match the client’s first render (causes errors/flicker).

Question 5

(Performance & Architecture)

Payload Bloat

Answer 5

Sending too much unnecessary JavaScript or JSON to the client.

Question 6

(TypeScript Soundness)

Exhaustiveness Checking
or Exhaustive Checking

Answer 6

Using the never type to ensure a switch statement handles every possible case in a union.

Question 7

(TypeScript Soundness)

Type Narrowing

Answer 7

The process of moving from a broad type (like string | number) to a specific one through logic.

Question 8

(TypeScript Soundness)

Branded Types / Nominal Typing

Answer 8

Using TypeScript to distinguish between two identical types (eg., a UserId string vs a PostId string).

Question 9

(Testing & A11y)

Implementation Leakage

Answer 9

A test that breaks because of how the code is written, rather than what the code does for the user.

Question 10

(Testing & A11y)

Flaky Tests

Answer 10

Tests that pass or fail inconsistently due to timing issues (like setTimeout).

Question 11

(Testing & A11y)

Accessible Name

Answer 11

The text a screen reader announces for an element (calculated from labels, alt text, or ARIA).

Question 12

(Testing & A11y)

Confidence Score

Answer 12

How much a test actually proves the feature works in the real world.