Data Partitioning and Sharding Questions

Techniques and operational practices for horizontally partitioning data across multiple database instances or storage nodes to achieve scale, improve performance, and manage growth. Includes selection and design of partition and shard keys to evenly distribute load and avoid hotspots, with range based, hash based, and directory based approaches and consistent hashing mechanisms. Covers handling uneven distribution and data skew, hotspot detection and mitigation, and the impact of partitioning on query patterns such as joins and cross shard queries. Explains implications for transactions and consistency, including transactional boundaries that span partitions and approaches to distributed transactions and compensation. Describes resharding and online data migration strategies, rolling rebalances, and methods to minimize downtime and data movement. Emphasizes operational concerns including shard management, automation, monitoring and alerting, failure recovery, and performance tuning. Discusses trade offs between simplicity, latency, throughput, and operational complexity and highlights considerations for both transactional and analytical workloads, including routing, caching, and coordination patterns.

HardTechnical

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Design a minimal-downtime rolling rebalancing procedure across 1000 shards when an availability zone degrades and you must evacuate shards to other zones. Include steps to preserve consistency, reduce network spikes, and coordinate with load balancers and clients.

MediumTechnical

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Compare directory-based sharding (shard map) and consistent hashing in terms of hotspot mitigation, resharding complexity, and operational visibility. Recommend one when tenant isolation and predictable performance are critical.

HardSystem Design

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Design a sharded architecture for an online payment gateway that must handle 10,000 TPS sustained and support transactional guarantees for payment state transitions. Describe shard key choice, how you'd minimize cross-shard transactions, failover strategy, and how to audit correctness.

MediumTechnical

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You have the following simplified order table:

sql

orders(order_id PK, customer_id, created_at TIMESTAMP, total DECIMAL)

Traffic: 10M customers, frequent reads by customer_id and occasional global reports. Recommend a shard key and partitioning approach (range/hash/directory) and explain how you would support efficient customer-scoped queries and occasional global aggregation.

HardTechnical

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Write a post-incident action plan and proposed architecture changes after a resharding-induced outage that caused inconsistent writes across several shards. Include root-cause analysis steps, immediate fixes, medium-term mitigations, and long-term architectural changes you'd recommend to avoid recurrence.

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