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What is the difference between S3 and HDFS?

Cloud/Toolshard0.6 min read

S3: Object storage—durable, highly available, decoupled from compute. Pay-per-use, virtually unlimited scale. Eventual consistency (now strong for new overwrites). No data locality. HDFS: Distributed file system—block-based, colocated with compute nodes. Data locality reduces...

🤖 Analyze Your Answer
Frequency
Low
Asked at 3 companies
Category
179
questions in Cloud/Tools
Difficulty Split
104E|27M|48H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
EYIncedoTech Mahindra
Interview Pro Tip

Red Flag: Saying 'HDFS is better' or 'S3 is better' without context. Pro-Move: Discussing migration trade-offs and when each is appropriate—shows architectural judgment.

Why This Question Matters

This hard-level Cloud/Tools question appears frequently in data engineering interviews at companies like EY, Incedo, Tech Mahindra. While less common, it tests deeper understanding that distinguishes strong candidates.

How to Approach This

This is a senior-level question that tests architectural thinking. Lead with the high-level design, then drill into specifics. Discuss trade-offs explicitly - there is rarely one correct answer. Show awareness of scale, fault tolerance, and operational complexity.

Expert Answer
115 words

S3: Object storage—durable, highly available, decoupled from compute. Pay-per-use, virtually unlimited scale. Eventual consistency (now strong for new overwrites). No data locality. HDFS: Distributed file system—block-based, colocated with compute nodes. Data locality reduces network I/O; strong consistency. Requires cluster management. Why it matters: S3 enables cloud-native, serverless patterns (Lambda, Glue, Athena); HDFS optimizes for batch processing where locality matters. Scalability: S3 scales transparently; HDFS requires adding nodes. Cost: S3 has no compute cost when idle; HDFS clusters run 24/7. Trade-off: Migrating from HDFS to S3 reduces ops but may require query and tool changes (e.g., Hive to Athena). For new workloads, S3 is the default; HDFS remains for on-prem Hadoop or legacy systems requiring locality.

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