Top 10 API Design Questions Asked by Product-Based Companies

Low-Level Design of YouTube: How Video Recommendations Are Powered

18/01/2025

Low-Level Design of Snapchat: How Stories and Snaps Work

16/01/2025

Low-Level Design of TikTok: Behind the Scenes of Short Video Processing

16/01/2025

Low-Level Design of Twitter: How Tweets Are Processed and Delivered

15/01/2025

Understanding the Low-Level Design of Facebook’s News Feed Algorithm

15/01/2025

Our Top Selling Courses

APIs (Application Programming Interfaces) are at the heart of modern software development, powering communication between different systems. For product-based companies, API design is a critical area that ensures scalable, efficient, and secure software solutions. In this blog, we’ll explore the Top 10 API Design Questions Asked by Product-Based Companies and provide actionable insights to ace these interview questions.

1. What Is REST, and How Does It Differ from SOAP?

Understanding REST and SOAP

REST (Representational State Transfer) and SOAP (Simple Object Access Protocol) are two prominent architectural styles used in API development. REST is a lightweight, stateless, and scalable approach, while SOAP is protocol-heavy and relies on XML for messaging.

Key Differences Between REST and SOAP

Protocol: REST uses HTTP, while SOAP is a protocol-based approach.
Data Formats: REST supports JSON, XML, and other formats, whereas SOAP is XML-exclusive.
Performance: REST is faster and more efficient, while SOAP ensures better security with built-in WS-Security.

Feature	REST	SOAP
Protocol	HTTP/HTTPS	HTTP, SMTP, TCP
Message Format	JSON, XML, YAML	XML
State Management	Stateless	Stateful

Recommended Topic: Key System Design Questions for Tech Interviews

2. How Do You Handle Versioning in APIs?

Importance of API Versioning

API versioning allows developers to introduce changes without disrupting existing clients. This ensures backward compatibility and smooth transitions.

Methods for Implementing API Versioning

URL Versioning: Adding versions in the URL (e.g., /v1/resource).
Header Versioning: Using custom headers to specify versions.
Query Parameters: Adding a version parameter in API requests.

Benefits of Each Method

URL Versioning: Simple and easy to understand.
Header Versioning: Keeps URLs clean and organized.
Query Parameters: Flexible for clients to use dynamically.

Versioning Method	Example	Pros	Cons
URL	/api/v1/users	Easy to implement	Clutters URLs
Header	Accept: application/v1	Cleaner implementation	Requires header parsing
Query Parameter	/api/users?version=1	Flexible for clients	Slightly harder to debug

Also Read: Top 20 API Design Interview Questions

3. How Would You Secure an API?

Core Security Principles

APIs must be protected against unauthorized access, data breaches, and malicious attacks. This involves authentication, authorization, and encryption.

Best Practices for API Security

Authentication: Use OAuth 2.0 or API keys for verifying users.
Rate Limiting: Prevent misuse by limiting API requests.
Encryption: Use HTTPS and TLS for data transmission.
Input Validation: Validate all inputs to prevent SQL injection.

Checklist for API Security

Implement OAuth 2.0 for secure authentication.
Use HTTPS for all communications.
Validate and sanitize inputs.
Enable rate limiting to avoid DDoS attacks.

Recommended Topic: Top 15 Facebook Low-Level Design Questions

4. How Do You Ensure Scalability in API Design?

Strategies for API Scalability

Scalability ensures that an API can handle increased traffic without degrading performance. Here are some methods:

Caching: Reduce server load by caching frequent responses.
Load Balancing: Distribute traffic across multiple servers.
Asynchronous Processing: Use queues for handling long-running tasks.

Tools for API Scalability

Technique	Tools/Technologies
Caching	Redis, Memcached
Load Balancing	AWS Elastic Load Balancer
Queues	RabbitMQ, Kafka

5. What Are the Best Practices for Designing API Endpoints?

Guidelines for Endpoint Design

Consistency: Use consistent naming conventions (e.g., nouns for resources).
HTTP Verbs: Follow REST principles (e.g., GET, POST, PUT, DELETE).
Error Handling: Provide meaningful error messages and status codes.

Examples of Well-Designed Endpoints

Action	Endpoint	HTTP Method
Get User Info	/api/users/{id}	GET
Create User	/api/users	POST
Delete User	/api/users/{id}	DELETE

Recommended Topic: Top 15 System Design Frameworks in 2024

6. What Is the Difference Between Synchronous and Asynchronous APIs?

Core Differences

Synchronous APIs: Block the client until the server processes the request.
Asynchronous APIs: Allow the client to proceed while the server handles the request in the background.

Use Cases

Synchronous: Banking transactions or payment gateways.
Asynchronous: File uploads or notifications.

Feature	Synchronous	Asynchronous
Response Time	Immediate	Delayed
Use Case	Real-time interactions	Background tasks

Also Read: Common React Interview Questions

7. How Would You Implement Pagination in an API?

Benefits of Pagination

Pagination helps manage large datasets by delivering data in smaller chunks, improving performance and user experience.

Common Pagination Methods

Offset-Based: Specify the starting point (e.g., ?offset=10&limit=5).
Cursor-Based: Use unique identifiers to fetch the next set of results.

Comparison of Pagination Techniques

Method	Pros	Cons
Offset-Based	Simple to implement	Slower for large datasets
Cursor-Based	Faster for large datasets	Requires complex logic

Recommended Topic: Top 10 Full-Stack Interview Questions

8. How Do You Handle Errors in API Responses?

Effective Error Handling Strategies

Standardized Codes: Use HTTP status codes (e.g., 404 for not found, 500 for server errors).
Descriptive Messages: Provide clear and actionable error messages.

Example of Error Response

{

“error”: {

“code”: 404,

“message”: “User not found”,

“details”: “No user exists with the given ID.”

}

Also Read: Top 20 Software Frameworks for 2025

9. What Is the Role of API Gateways?

Key Functions of an API Gateway

API Gateways act as intermediaries, managing requests between clients and services. They provide:

Request Routing: Forward requests to appropriate services.
Authentication: Verify users and enforce security.
Monitoring: Track performance and usage.

Popular API Gateway Tools

AWS API Gateway
Kong
Apigee

10. What Are the Advantages of Using GraphQL Over REST?

Key Differences Between GraphQL and REST

GraphQL offers a flexible query language, allowing clients to fetch only the required data. In contrast, REST fetches predefined data structures.

Benefits of GraphQL

Data Efficiency: Fetch multiple resources in a single request.
Flexibility: Allows querying specific fields.
Versionless: No need for versioning due to its schema-based design.

Feature	REST	GraphQL
Data Fetching	Fixed endpoints	Dynamic queries
Flexibility	Limited	High
Over-fetching	Yes	No

Also Read: Top 15 Python ML Interview Questions

FAQs

What are the key considerations when designing APIs for scalability?

To design scalable APIs, you need to focus on load balancing, rate limiting, and efficient database access patterns. Employing these practices ensures that your API can handle increasing traffic seamlessly. For mastering such concepts, explore DSA and System Design Courses.

Why is versioning important in API design?

API versioning allows developers to introduce updates without breaking existing functionality. It ensures backward compatibility and a seamless user experience. To gain hands-on expertise in this, check out the Master DSA, Web Development & System Design Course.

How do you secure APIs against vulnerabilities?

Securing APIs involves implementing authentication, authorization, and encryption protocols, alongside regular vulnerability assessments. For in-depth learning, consider enrolling in the Web Development Course.

What are the best practices for API documentation?

Clear and comprehensive API documentation ensures smooth collaboration between teams and enhances developer experience. Learning frameworks like Swagger can make this process efficient. Learn more through the Data Science and DSA Courses.

How can you optimize API performance?

API performance can be optimized by employing caching, reducing payload size, and choosing efficient communication protocols. To dive deeper into these techniques, explore the DSA Course.

Accelerate your Path to a Product based Career

Boost your career or get hired at top product-based companies by joining our expertly crafted courses. Gain practical skills and real-world knowledge to help you succeed.