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Back-end Interview Questions
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1.
What is backend development?
2.
What is Node.js?
3.
Why is Node.js popular for backend development?
4.
What is the difference between synchronous and asynchronous code?
5.
What is Express.js?
6.
What is npm?
7.
How do you initialize a Node.js project?
8.
What is middleware in Express?
9.
What is routing in Express.js?
10.
What is the role of the req and res objects in Express?
11.
What is an API?
12.
What is a RESTful API?
13.
What does CRUD stand for?
14.
What is a GET request used for?
15.
What is a POST request used for?
16.
What status code represents success?
17.
What is the meaning of HTTP 404?
18.
What status code indicates a server error?
19.
How do you send JSON data in Express?
20.
What tool can you use to test APIs?
21.
What is a database?
22.
What is the difference between SQL and NoSQL?
23.
What is MongoDB?
24.
What is a collection in MongoDB?
25.
What is a document in MongoDB?
26.
What is Mongoose?
27.
How do you connect to MongoDB in Node.js?
28.
What does find() do in MongoDB?
29.
How do you insert data into MongoDB?
30.
What is a schema in Mongoose?
31.
What is authentication?
32.
What is authorization?
33.
What is JWT?
34.
How do you protect an API route?
35.
What is hashing?
36.
What library is used to hash passwords in Node.js?
37.
What are environment variables?
38.
What is CORS?
39.
How do you enable CORS in Express?
40.
What are HTTP-only cookies?
41.
What is version control and why is it important?
42.
What is a pull request?
43.
What is a package.json file?
44.
How do you start a Node.js server?
45.
What is a 3rd-party API?
46.
What is Postman used for?
47.
What is logging and why is it important?
48.
What is the role of .gitignore?
49.
How do you structure a basic Node.js project?
50.
How do you deploy a Node.js app?
51.
What is the difference between synchronous and asynchronous code in Node.js?
52.
How does the Node.js event loop work?
53.
Explain the concept of middleware in Express.js.
54.
What are streams in Node.js and when would you use them?
55.
What is the purpose of the next() function in Express middleware?
56.
What is the difference between SQL and NoSQL databases?
57.
Explain Mongoose schemas and models.
58.
What is indexing in databases and why is it important?
59.
What are transactions in MongoDB and when would you use them?
60.
What are aggregate pipelines in MongoDB?
61.
What is RESTful API and what are its core principles?
62.
Explain the purpose of status codes in an API.
63.
What are the best practices when designing REST APIs?
64.
How do you implement pagination in a REST API?
65.
How do you handle validation in an Express app?
66.
What is the difference between authentication and authorization?
67.
How does JWT work for authentication?
68.
Where should access and refresh tokens be stored in the frontend?
69.
What is role-based access control (RBAC)?
70.
How do you protect routes in Express?
71.
How do you write unit tests in a backend app?
72.
What is the difference between unit and integration testing?
73.
How can you mock a database in tests?
74.
What tools do you use for testing an Express API?
75.
How do you debug memory leaks in Node.js?
76.
How do you handle performance bottlenecks in backend applications?
77.
What is caching and how is it implemented in backend apps?
78.
What are memory leaks and how do they occur in Node.js?
79.
What is the benefit of using a queue system like RabbitMQ or Bull?
80.
How do you ensure database performance under high load?
81.
How do you set up a CI/CD pipeline for a Node.js app?
82.
What are environment variables and how are they used?
83.
What is Docker and how is it used in backend development?
84.
What are some security best practices for deployment?
85.
How do you monitor backend performance in production?
86.
How would you design a scalable file upload service?
87.
What is horizontal vs vertical scaling?
88.
What are web sockets and when would you use them?
89.
What is load balancing and how does it help?
90.
How would you handle sudden traffic spikes?
91.
What is rate limiting and how do you implement it?
92.
What is CSRF and how do you prevent it?
93.
How do you implement logging in Node.js?
94.
What is graceful shutdown in backend apps?
95.
How do you handle errors in Express?
96.
What is the purpose of process.nextTick() in Node.js?
97.
How do you deal with API versioning?
98.
What is HATEOAS in REST APIs?
99.
How do you secure sensitive data like passwords?
100.
How do you prevent common Node.js security issues?
101.
What is the difference between monolithic and microservices architecture?
102.
How do you design a scalable backend system?
103.
What is the role of load balancers in backend architecture?
104.
How do you ensure high availability and fault tolerance?
105.
What is the CAP theorem and how does it apply to backend systems?
106.
Explain how the Node.js event loop works.
107.
What are the limitations of single-threaded architecture in Node.js?
108.
How does Node.js handle asynchronous operations under the hood?
109.
What is the difference between process.nextTick(), setImmediate(), and setTimeout()?
110.
How do worker threads improve performance in Node.js?
111.
What is middleware chaining in Express.js?
112.
How would you handle global error handling in Express?
113.
How can you organize a large Express.js application?
114.
What is the difference between app.use() and app.get()/app.post()?
115.
How would you implement rate-limiting middleware?
116.
When should you choose NoSQL like MongoDB over SQL?
117.
What are the trade-offs of embedding vs referencing in MongoDB?
118.
How would you handle schema changes in production MongoDB?
119.
How do indexes affect MongoDB performance?
120.
What is a MongoDB transaction and when to use it?
121.
How does JWT authentication work?
122.
What is the difference between OAuth2 and JWT?
123.
How do you implement refresh tokens securely?
124.
How would you protect admin-only routes in an API?
125.
What are common auth vulnerabilities and how do you prevent them?
126.
How do you version REST APIs?
127.
PUT vs PATCH – what's the difference?
128.
How do you implement API rate limiting?
129.
How do you document APIs properly?
130.
How do you design an API gateway?
131.
How do you structure backend tests?
132.
How do you mock MongoDB or APIs in tests?
133.
How do you detect memory leaks in Node.js?
134.
What is Test-Driven Development (TDD)?
135.
Which logs/metrics do you monitor in production?
136.
How do you set up CI/CD for a Node.js app?
137.
Difference between Docker and VM?
138.
How do you manage environment variables securely?
139.
What is Infrastructure as Code (IaC)?
140.
How do you deploy a scalable backend system?
141.
How do you implement caching in a backend app?
142.
Redis vs in-process cache?
143.
How do you profile backend bottlenecks?
144.
How do you optimize cold start times?
145.
How do you handle DB overload on reads/writes?
146.
What are the OWASP Top 10 backend risks?
147.
How to prevent injection attacks?
148.
How to handle file uploads securely?
149.
What is CORS and how to secure it?
150.
How to secure microservices communication?