Database Selection and Trade Offs Questions

How to evaluate and choose data storage systems and architectures based on workload characteristics and business constraints. Coverage includes differences between relational and nonrelational families such as document stores, key value stores, wide column stores, graph databases, time series databases, and search engines; mapping query patterns and latency requirements to storage options; trade offs between strong consistency and eventual consistency and their impact on availability and complexity; partition key design, replication strategies, and high availability considerations; operational concerns including backups, monitoring, vendor and cost trade offs, migration or hybrid strategies, and when to adopt polyglot persistence. Senior level discussion includes selecting specific managed services and reasoning about expected load patterns, failure modes, and operational burden.

EasyTechnical

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Describe the purpose of a partition key and how it differs from a primary key. Provide examples of bad partition key choices that lead to hot partitions and simple mitigation strategies such as key salting or composite keys. Explain implications for range queries.

HardTechnical

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Architect a change-data-capture pipeline to reliably replicate transactional database changes into a search index and an analytics data lake. Address ordering guarantees, exactly-once delivery or deduplication, schema evolution handling, backfill processes, latency targets, and how to replay or repair after outages.

HardSystem Design

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Design partitioning, caching, and write strategies to mitigate hot keys for a social feed service with unpredictable viral spikes. Include hash-based sharding, range sharding tradeoffs, write fanout versus fanout-on-read, cache invalidation approaches, rate limiting, backpressure to producers, and fallback behavior during overloads.

HardSystem Design

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Design a globally distributed database across three regions for a social app with 100M users that must optimize read locality and provide global eventual consistency. Describe replication topology, conflict resolution approach, leader election, failover behavior, data residency considerations, and how you would measure compliance with an SLA of 99.99% and RPO 5 seconds.

MediumTechnical

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Explain practical implications of eventual consistency for user-facing reads: stale reads, out-of-order updates, and cache coherence. Suggest design patterns to mitigate UX issues such as read-your-writes, session affinity, write-through caches, and tombstone propagation, and when to use each.

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