Common Mistakes That Cost You the Offer (And How to Avoid Them)

6 common mistakes candidates do and how you can fix them before your next interview

Technical interviews aren’t just about solving problems, they test how you think, communicate, handle pressure, and solve problems. Many candidates fail not because they lack knowledge but because of small mistakes that snowball into rejection.

I have failed >50% of the interviews I appeared for and compiled this list of mistakes based on the feedback I’ve received through multiple years

Let’s break down these 6 critical mistakes and how you can fix them before your next interview

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🚨 Mistake #1: Jumping Straight Into Coding Without a Plan

❌ The Problem:

You hear the problem, you feel confident, and start coding immediately. Halfway through your solution, you realize that have you missed a key detail, and now you’re stuck refactoring your entire solution.

✅ The Fix:

🔹 Clarify the problem: Ask questions and don’t assume anything. Even if it sounds simple, check constraints like input size, null values, duplicates, etc.
🔹 Think out loud: Walk through your approach before touching the keyboard. This helps interviewers understand your thought process.
🔹 Write pseudocode first: If your approach makes sense in plain English, it’s much easier to translate into code. Get an alignment from the interviewer before proceeding to write actual code

📝 Example:
🔸 Instead of jumping into coding a “shortest path” problem, confirm: Is it a weighted graph? Can nodes be revisited? What’s the expected output format?

If you want a structured plan for cracking top product-based companies, you should check out the Transformer and Evolve programs by Bosscoder Academy

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🚨 Mistake #2: Ignoring Edge Cases and Optimizations

❌ The Problem:

You solve the basic problem but forget to test tricky cases like empty lists, repeated numbers, and very large inputs. The interviewer adds an edge case, and your solution fails instantly.

✅ The Fix:

🔹 Think of edge cases before coding. Common ones include:
✔️ Empty inputs
✔️ Large values (scalability concerns)
✔️ Duplicates or negative numbers
✔️ Special cases (single element, already sorted)

🔹 Test your code before saying “done.” Run through at least 2-3 different test cases manually.

📝 Example:
🔸 If solving a “merge two sorted lists” problem, ask: What happens if one list is empty?

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🚨 Mistake #3: Poor Communication During the Interview

❌ The Problem:

You stay silent while solving the problem. The interviewer has no idea what you’re thinking and assumes you're lost.

✅ The Fix:

🔹 Talk through your thought process: Interviewers evaluate your reasoning, not just the final answer.
🔹 Explain your trade-offs: If you use a hash table instead of a list, say why.
🔹 If stuck, don’t panic and talk it out: Many interviewers will give hints if you explain what’s confusing you.

📝 Example:
🔸 Instead of silently writing O(NlogN) sorting, say: "I could use a hash set for O(n) time, but it would take extra space. If memory is a concern, a two-pointer approach works too."

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🚨 Mistake #4: No Structure In System Design Answers

❌ The Problem:

Instead of structuring your response, you just mention different system components with no clear approach.

✅ The Fix:

🔹 Start with requirements. Ask: Are we optimizing for scale, consistency, or low latency?
🔹 Break it down step by step:
✔️ Estimates: How much storage and compute needed?
✔️ Data flow: How do requests move through the system?
✔️ Storage choice: SQL vs NoSQL?
✔️ Scaling strategy: Load balancing, caching, replication?

📝 Example:
🔸 If designing a URL shortener, clarify: Should links expire? How many requests per second? Then structure your answer around storage, API design, and scaling.

For more such nuances and cracking top product-based companies, do check out the Transformer and Evolve programs by Bosscoder Academy

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🚨 Mistake #5: Not Practicing in a Real Interview Setting

❌ The Problem:

You solve LeetCode problems daily, but during an actual interview, the pressure makes you freeze.

✅ The Fix:

🔹 Do mock interviews: Practice with platforms like Bosscoder Academy or with a peer.
🔹 Time yourself: Try solving problems in 30-40 minutes with a strict timer.
🔹 Simulate real interview conditions: Code on a whiteboard or shared doc instead of your IDE.

📝 Example:
🔸 Keep a timer on your desk and explain your solution out loud as you write it, dry run on multiple test cases just like in a real interview.

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🚨 Mistake #6: Rushing Through Behavioral Questions

❌ The Problem:

You focus only on coding prep and fumble when asked about behavior questions

✅ The Fix:

🔹 Prepare multiple stories beforehand and know which story to tell on what question. Practice in front of a friend or mirror. Look Confident
🔹 Use the STAR method when answering:
✔️ Situation – What was the problem?
✔️ Task – What was your role?
✔️ Action – What did you do?
✔️ Result – What was the outcome?

📝 Example:
🔸 Instead of saying "I worked on a scaling issue," say:
"Our system crashed under high traffic. I optimized the DB queries, reducing response time by 40%, and implemented caching, cutting server costs by 30%."

💡 Want to learn from the best in industry? check out the Transformer and Evolve programs by Bosscoder Academy

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I shared my “Interview Preparation Strategy” article a while back to share how I prepared for interviews