Master the most common coding interview patterns to ace your technical rounds.
For technical interview preparation, our system design guide is essential reading.
Don't neglect behavioral preparation — see our behavioral interview guide.
Your resume is the first impression — get it right with our resume guide.
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"@type": "BlogPosting",
"headline": "Data Stream Problems: Median, Running Stats, and Reservoir Sampling",
"description": "Interview patterns for data streams \u2014 finding median from a data stream with two heaps, running mean/variance, reservoir sampling for random sampling.",
"datePublished": "2026-03-20",
"author": {
"@type": "Organization",
"name": "CodeSwiftr Team"
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"url": "https://codeswiftr.com/blog/interview-data-stream-problems"
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{
"@type": "Question",
"name": "How should I structure my technical interview preparation?",
"acceptedAnswer": {
"@type": "Answer",
"text": "A structured 8–12 week preparation plan is most effective. Week 1–4: data structures and algorithms fundamentals using LeetCode easy-to-medium problems. Week 5–7: system design patterns using resources like the System Design Primer. Week 8–10: behavioral interview preparation with the STAR method. Week 11–12: company-specific mock interviews and review. Consistency matters more than intensity — 1–2 hours per day beats irregular all-day sessions."
}
},
{
"@type": "Question",
"name": "What is the STAR method and how should I use it in interviews?",
"acceptedAnswer": {
"@type": "Answer",
"text": "STAR stands for Situation, Task, Action, Result. It is the standard framework for answering behavioral interview questions. Situation: briefly describe the context (1–2 sentences). Task: explain your specific responsibility. Action: detail the steps you personally took — use 'I' not 'we'. Result: quantify the outcome wherever possible (e.g., 'reduced latency by 40%', 'increased conversion rate by 12%'). Keep each answer to 2–3 minutes."
}
},
{
"@type": "Question",
"name": "What LeetCode difficulty level should I focus on?",
"acceptedAnswer": {
"@type": "Answer",
"text": "For FAANG interviews, focus 20% on easy, 60% on medium, and 20% on hard problems. Easy problems build speed and confidence. Medium problems represent the most common interview difficulty at top companies. Hard problems appear mostly at Google, Meta, and specialised algorithmic roles. Do not skip easy problems — many candidates fail by overthinking genuinely simple questions that require clean, efficient solutions."
}
},
{
"@type": "Question",
"name": "How important is system design compared to coding in tech interviews?",
"acceptedAnswer": {
"@type": "Answer",
"text": "At mid-level and senior positions, system design carries equal or greater weight than coding. Entry-level and new-grad interviews are predominantly coding-focused. Senior and staff-level interviews dedicate one or two full rounds to system design. Master the core components: load balancers, databases (SQL vs NoSQL trade-offs), caches (Redis, Memcached), message queues (Kafka, SQS), CDNs, and API design. Practice designing real systems you use daily — the interviewer values practical reasoning over textbook answers."
}
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]
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