Coding Interview Preparation

💻 Coding Interview Questions

1️⃣ What is a linked list?
Answer: A linear data structure where elements point to the next element.

2️⃣ Singly vs Doubly Linked List?
Answer: Singly points forward; doubly points forward and backward.

3️⃣ What is a circular linked list?
Answer: The last node points back to the first node.

4️⃣ What is a stack?
Answer: LIFO data structure (Last In, First Out).

5️⃣ What is a queue?
Answer: FIFO data structure (First In, First Out).

6️⃣ What is a priority queue?
Answer: Elements are dequeued based on priority, not insertion order.

7️⃣ What is a deque?
Answer: Double-ended queue, insert/delete from both ends.

8️⃣ What is a hash map?
Answer: Stores key-value pairs for fast retrieval.

9️⃣ What is collision in hash tables?
Answer: Two keys map to the same index; resolved using chaining or open addressing.

🔟 What is a binary tree?
Answer: Tree data structure where each node has at most two children.

The Sneaky Bug Hunt

🗯 Scenario: You are handed a piece of code and told,

Something here is wrong.

No hints.

👉 Do this: Slow down and read the code aloud while explaining what each section is supposed to do. Then create a tiny test case and trace variable values step by step. Pay special attention to boundary conditions and loop exits.

❌ Avoid guessing the bug too early. Interviewers often care more about your debugging discipline than how fast you spot the issue.

❔Interviewer:

How would you design a cache system?

✅Answer:

I would begin by clarifying access patterns, data volatility, and consistency requirements.

At a high level, the system would include a fast in-memory cache layer such as Redis in front of the primary database. I would define an eviction policy like LRU to manage memory usage and implement TTLs for data freshness.

I would also plan for cache invalidation strategies, cache stampede protection, and monitoring of hit rate. The design trade-off typically balances freshness, consistency, and performance.

💻 Coding Interview Questions

1️⃣ What is recursion?
Answer: When a function calls itself until a base condition is met.

2️⃣ What is iteration?
Answer: Repeating a set of instructions using loops (for, while).

3️⃣ Recursion vs Iteration?
Answer: Recursion uses function calls; iteration uses loops. Recursion may use more memory.

4️⃣ What is a base case?
Answer: The condition that stops recursion.

5️⃣ What is tail recursion?
Answer: A recursion where the recursive call is the last operation.

6️⃣ What is a divide-and-conquer algorithm?
Answer: Break problem into smaller sub-problems, solve recursively, combine results.

7️⃣ What is dynamic programming?
Answer: Solving problems by storing intermediate results to avoid recomputation.

8️⃣ What is memoization?
Answer: Storing function results to speed up future calls.

9️⃣ What is greedy algorithm?
Answer: Make the locally optimal choice at each step to find global optimum.

🔟 What is backtracking?
Answer: Trying all possibilities and discarding invalid paths to find a solution.

❔Interviewer:

How would you detect a memory leak in a production system?

✅ Answer:

I would start by monitoring memory usage trends over time using application metrics and system level tools. A steadily increasing memory footprint without release is usually a strong signal.

Next, I would capture heap dumps or use profiling tools to identify objects that are not being garbage collected. From there, I would trace back to the code paths retaining those references.

After fixing the root cause, I would add monitoring and alerts to detect abnormal memory growth early in the future. Prevention through observability is just as important as the fix itself.

The Failure Question

🗯 Scenario:

Tell me about a time you failed.

This one always feels loaded.

👉 Do this: Choose a genuine example and keep the setup brief. Focus most of your answer on what you changed afterward and the measurable improvement that followed. Use a simple structure: situation, mistake, lesson, growth.

❌ Avoid blaming teammates or circumstances. Interviewers are listening for ownership and self awareness far more than the failure itself.

❔Interviewer:

How do you approach debugging a system you did not build?

✅ Answer:

When debugging an unfamiliar system, I start by understanding the high level architecture and the data flow between components.

Next, I reproduce the issue in a controlled environment and use logs, metrics, and traces to narrow down where the failure occurs. I form hypotheses and validate them incrementally rather than making broad changes.

Throughout the process, I document findings and communicate with team members who have context. This structured approach helps reduce guesswork and speeds up root cause identification.

💻 Coding Interview Questions

1️⃣ What is an API?
Answer: A set of rules that allows software to communicate with other software.

2️⃣ What is REST?
Answer: An architectural style for building web services using HTTP.

3️⃣ What is HTTP?
Answer: A protocol for transferring data over the web.

4️⃣ GET vs POST?
Answer: GET retrieves data; POST sends data to the server.

5️⃣ What is a status code 404?
Answer: Resource not found.

6️⃣ What is JSON?
Answer: A lightweight data-interchange format.

7️⃣ What is authentication?
Answer: Verifying user identity.

8️⃣ What is authorization?
Answer: Granting permissions after authentication.

9️⃣ What is a cookie?
Answer: Small data stored in the browser.

🔟 What is a session?
Answer: Server-side storage of user data during interaction.

❔Interviewer:

What is the difference between REST and RPC?

✅ Answer:

REST is an architectural style that models interactions around resources using standard HTTP methods such as GET, POST, PUT, and DELETE. It emphasizes stateless communication and resource oriented design.

RPC, or Remote Procedure Call, focuses on invoking actions or functions on a remote server as if they were local calls. It is typically more operation focused rather than resource focused.

REST is generally preferred for public web APIs due to its simplicity and cache friendliness, while RPC based approaches like gRPC are often used in internal microservices where performance and strong contracts are more important.

The Clarification You Forgot to Ask

🗯 Scenario: Halfway through coding, the interviewer says,

What about negative numbers?

Your solution breaks. You knew you should have asked more questions.

👉Do this: Before writing code, lock in the habit of asking at least three clarifying questions. Confirm input ranges, data types, and whether duplicates or negatives are possible. Technically, this protects you from hidden constraints that often change the entire approach. Strong candidates reduce surprises early.

❔Interviewer:

How do you prioritize tasks when everything seems urgent?

✅ Answer:

When multiple tasks are urgent, I first evaluate impact and urgency separately. I prioritize work that affects customers or production stability the most.

I also communicate early with stakeholders to align expectations and avoid silent trade offs. If necessary, I break work into smaller deliverables to show progress quickly.

This structured prioritization helps ensure that the most critical issues are addressed first while maintaining transparency with the team.

AI vs Machine Learning vs Deep Learning vs Generative AI

❔Interviewer:

How does database indexing improve performance?

✅ Answer:

Database indexing improves performance by creating a data structure, typically a B-tree or hash based structure, that allows the database engine to locate rows quickly without scanning the entire table.

Without an index, queries often require full table scans, which are O(n). With a proper index, lookups can be reduced to O(log n) or even O(1) depending on the index type.

However, indexes come with trade offs. They consume additional storage and can slow down write operations because the index must be updated whenever the data changes. Therefore, indexes should be added selectively based on query patterns.

The Final Question Trap

🗯 Scenario: The interviewer smiles and says,

Do you have any questions for us?

👉 Do this: Always have one thoughtful question ready. Ask about the team’s biggest technical challenge or what success looks like in the first six months. Sharp questions make you memorable long after the coding part ends.

💻 Coding Interview Questions

1️⃣ What is a pointer?
Answer: A variable that stores the memory address of another variable.

2️⃣ What is memory allocation?
Answer: The process of reserving memory for program execution.

3️⃣ Stack vs Heap memory?
Answer: Stack is fast and automatic; heap is dynamic and manually managed.

4️⃣ What is garbage collection?
Answer: Automatic memory cleanup of unused objects.

5️⃣ What is a deadlock?
Answer: When processes wait forever for resources held by each other.

6️⃣ What is multithreading?
Answer: Running multiple threads concurrently within a process.

7️⃣ What is synchronization?
Answer: Controlling access to shared resources in concurrent programs.

8️⃣ What is a race condition?
Answer: When multiple threads access shared data unsafely.

9️⃣ What is a process?
Answer: An independent program in execution.

🔟 What is a thread?
Answer: The smallest unit of execution within a process.

The Memory Usage Question

🗯 Scenario: After solving the problem, the interviewer asks about space complexity and you did not track it.

👉 Do this: Always mention both time and space when presenting a solution. Count auxiliary data structures and recursion stack if present. Technically, many candidates forget that recursion adds implicit space. Calling this out makes you look much more thorough.