APIs & distributed systems · topic 2 of 4

JSON

50 curated JSON interview questions — syntax, parsing, schema validation, and JSON vs XML, with worked answers for every experience level.

Questions below are grouped from foundations to advanced. Work top to bottom if the topic is new to you, or jump to a level if you are brushing up.

Questions: 26
Difficulty mix: 15 easy · 10 medium · 1 hard

Topics covered

Objects & Arrays5
Parsing3
REST APIs3
Advanced3
JSON vs XML2
Basics2
Syntax2
Serialization2
Validation1
Schema1
Performance1
Security1

Foundations

Easy · 15 questions

Definitions and building blocks — start here if the topic is new to you.

Why did JSON largely replace XML for APIs?
JSON vs XMLEasy
What is JSON?
BasicsEasy
Why is JSON so widely used?
BasicsEasy
What are the key structural differences between JSON and XML?
JSON vs XMLEasy
What data types does JSON support?
SyntaxEasy
What are the syntax rules of valid JSON?
SyntaxEasy
What is the difference between a JSON object and a JSON array?
Objects & ArraysEasy
How do nested JSON objects work?
Objects & ArraysEasy
How are JSON arrays used and what can they contain?
Objects & ArraysEasy
What is JSON parsing?
ParsingEasy
What is the difference between serialization and deserialization?
SerializationEasy
What is pretty-printing JSON and how do you do it?
SerializationEasy
How is JSON used in REST APIs?
REST APIsEasy
What is the difference between request JSON and response JSON?
REST APIsEasy
How do HTTP status codes work together with JSON responses?
REST APIsEasy

Core concepts

Medium · 10 questions

The questions most interviews spend their time on: how it works and when to use it.

How do you safely access values in nested JSON?
Objects & ArraysMedium
What does it mean to flatten JSON and when would you do it?
Objects & ArraysMedium
What are common JSON parsing errors and their causes?
ParsingMedium
How do you handle invalid or malformed JSON?
ParsingMedium
How do you validate incoming JSON?
ValidationMedium
What is JSON Schema and why is it useful?
SchemaMedium
What are JSON security best practices?
SecurityMedium
What is the difference between JSON and BSON?
AdvancedMedium
How does JSON structure a JWT (JSON Web Token)?
AdvancedMedium
What are common JSON interview scenarios and how do you approach them?
AdvancedMedium

Advanced

Hard · 1 question

Internals, trade-offs and edge cases — useful for senior rounds and follow-ups.

How do you handle large JSON payloads efficiently?
PerformanceHard

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Topics covered

Foundations

Why did JSON largely replace XML for APIs?

What is JSON?

Why is JSON so widely used?

What are the key structural differences between JSON and XML?

What data types does JSON support?

What are the syntax rules of valid JSON?

What is the difference between a JSON object and a JSON array?

How do nested JSON objects work?

How are JSON arrays used and what can they contain?

What is JSON parsing?

What is the difference between serialization and deserialization?

What is pretty-printing JSON and how do you do it?

How is JSON used in REST APIs?

What is the difference between request JSON and response JSON?

How do HTTP status codes work together with JSON responses?

Core concepts

How do you safely access values in nested JSON?

What does it mean to flatten JSON and when would you do it?

What are common JSON parsing errors and their causes?

How do you handle invalid or malformed JSON?

How do you validate incoming JSON?

What is JSON Schema and why is it useful?

What are JSON security best practices?

What is the difference between JSON and BSON?

How does JSON structure a JWT (JSON Web Token)?

What are common JSON interview scenarios and how do you approach them?

Advanced

How do you handle large JSON payloads efficiently?