Easy interview questions in Backend Dev
Explain Python type hints and their importance in FastAPI
Python type hints describe expected data, but Python itself does not enforce them. FastAPI reads those annotations with Pydantic to parse and validate requests and generate OpenAPI documentation. A strong answer separates language syntax from framework behavior.
How does Node.js handle thousands of connections on one thread?
This tests non-blocking I/O: Node.js runs one thread for an event loop while the OS handles sockets via epoll or IOCP, resuming callbacks when data arrives. Mention the thread pool for DNS and fs work. A red flag is claiming threads spawn per request.
Compare Go's GC and Rust's ownership across performance, productivity, and safety
This tests memory-model trade-offs. Contrast Rust's compile-time ownership for deterministic, zero-cost safety against Go's GC, which optimizes simplicity and onboarding but adds runtime overhead. Red flag: calling one strictly superior.
What is the difference between primary, foreign, and unique keys?
This tests relational integrity basics. Answer: primary keys identify rows, foreign keys reference tables, and unique keys are alternate candidates. Red flag: saying unique keys are just for indexing or omitting a non-PK example like email.
Refactoring under Go simplicity versus Rust correctness
Rust's type system catches broken invariants at compile time so refactors are guided; Go's explicitness keeps code readable but shifts safety to tests and discipline.
What is the difference between def and async def in Python and FastAPI?
Tests event-loop boundaries: async def yields control via await for non-blocking I/O, def runs in a threadpool. Use async def only with async libraries; def covers blocking calls. Red flag: claiming async is automatically faster or awaiting inside def.
Explain ACID properties and why they matter for banking or e-commerce
Define each as a failure-handling guarantee; show how partial commits cause double-spending.
What is the difference between DDL and DML in SQL?
DDL shapes schema with CREATE or ALTER; DML handles row-level data with SELECT, INSERT, UPDATE, or DELETE.
dependencies vs devDependencies in package.json
Dependencies ship and run in production; devDependencies are only for development; omitted with npm install --production.
How does Go's variable declaration and mutability differ from Rust?
Contrast Rust let (immutable) and let mut (mutable) with Go var and := (mutable), noting Go uses const for immutability.
Resolving core vs relative module specifiers
'fs' is a built-in core module loaded by name with top priority; './my-file.js' is a relative path resolved from the current file.
Write a 1-to-5 loop in Go and Rust
Write Go's three-clause for, write Rust's 1..=5 range iterator, and contrast statement iteration with iterator consumption.
What is the purpose of @app.get("/") in FastAPI?
Tests your understanding of FastAPI routing. A strong answer explains that the decorator binds an HTTP method and path to a Python function, registers it in the app's route table, and builds OpenAPI metadata.
How do you define and access a FastAPI path parameter?
Tests FastAPI route-to-function binding. Good answer: curly-brace syntax in the decorator path, a matching typed function argument, and awareness that FastAPI auto-extracts and converts the value.
Normalizing a flat orders table to 3NF
Split repeating data, remove partial dependencies, remove transitive dependencies, define keys.
Modeling one-to-many versus many-to-many relationships
One-to-many uses a foreign key on the many side; many-to-many needs a junction table with two foreign keys.
The three states of a JavaScript Promise
Pending, fulfilled, rejected; settle is one-way and final; create with the executor calling resolve or reject, consume with then and catch.
How do you append to a Go slice and why reassign?
Tests slice headers and append reallocation. A strong answer reassigns the result (s = append(s, 4)), explains that append may allocate a new backing array, and warns that ignoring the return value drops elements. Red flag: calling append without assignment.
Define a WebEvent enum with PageLoad, PageUnload, and KeyPress
Tests Rust enum syntax: unit versus tuple variants. A good answer defines WebEvent with PageLoad, PageUnload, and KeyPress(char), then instantiates WebEvent::KeyPress('q'). A red flag is forgetting the double colon or using struct variant syntax.
Define a User struct and map of IDs to pointers
Tests Go struct and map pointer basics. Outline: define User with ID and Name, initialize map[int]*User with make, insert &User literals, and note shared mutation. Red flag: writing to a nil map or storing values instead of pointers.
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