IT interviews: the rounds and the fundamentals they test

BeginnerInterview Prep

Sample guide. Edit or replace it with your own material.

Most software and IT hiring processes follow the same pattern. Knowing what each round checks helps you prepare for the right things.

1. The usual rounds

Round	What it checks	How to prepare
Online assessment	Coding speed, aptitude, sometimes MCQs on CS basics	Timed practice on easy and medium problems
Technical round 1	Data structures, algorithms, one language in depth	Explain your approach aloud before coding
Technical round 2	Projects, CS fundamentals, sometimes basic design	Know every line on your resume
Managerial / HR	Communication, teamwork, motivation	Prepare stories using the STAR method

Experienced candidates (usually 3+ years) often get a system design round instead of, or as well as, a second coding round.

2. Coding rounds: what interviewers look for

Clarify first. Ask about input size, edge cases, and expected output before writing code.
Say the brute-force idea, then improve it. A working simple solution is better than an unfinished clever one.
State time and space complexity of your final solution, for example O(n log n) time, O(n) space.
Test with an example by tracing your code, including an edge case (empty input, one element, duplicates).

Topics that cover most fresher and junior questions: arrays and strings, hashing, two pointers, sliding window, stacks and queues, linked lists, binary search, trees (traversals, BST), recursion, and basic graphs (BFS/DFS).

3. Fundamentals that come up again and again

Object-oriented programming

The four ideas: encapsulation, abstraction, inheritance, polymorphism. Give a small example of each from code you have written.
Overloading (same name, different parameters, chosen at compile time) vs overriding (subclass replaces a parent method, chosen at run time).

Databases (SQL)

INNER JOIN returns only matching rows; LEFT JOIN returns all rows from the left table, with NULL where there is no match.
WHERE filters rows before grouping; HAVING filters groups after GROUP BY.
An index speeds up reads on the indexed column, but makes writes slightly slower and uses extra storage.

Operating systems

Process vs thread: a process has its own memory space; threads in the same process share memory, which makes them lighter but needs synchronisation.
Deadlock needs four conditions at the same time: mutual exclusion, hold and wait, no pre-emption, and circular wait. Breaking any one prevents it.

Networking and the web

What happens when you type a URL: DNS lookup → TCP connection → TLS handshake (for HTTPS) → HTTP request → server response → the browser renders the page.
TCP is connection-based and reliable (ordered, retransmitted); UDP is connectionless and faster, used where some loss is acceptable (video calls, games).

Git

git merge keeps both histories and adds a merge commit; git rebase replays your commits on top of another branch for a straight-line history.

4. “Tell me about your project”

Use this structure, in about two minutes:

Problem: what it solves and for whom.
Your role: what you built, not the whole team.
Tech choices: what you used and why.
A challenge: one real problem and how you solved it.
Result: numbers if you have them (users, speed-up, time saved).

Practice

Solve one easy problem today, timing yourself, and explain your solution aloud.
Write your two-minute project explanation and record yourself saying it.