Database Scalability and High Availability Questions

Architectural approaches and operational practices for scaling and maintaining database availability. Topics include vertical versus horizontal scaling trade offs; replication topologies, leader and follower roles, read replicas and replica lag; read write splitting and connection pooling; sharding and partitioning strategies including range based, hash based, and consistent hashing approaches; handling hot partitions and data skew; federation and multi database federation patterns; cache layers and cache invalidation; rebalancing and resharding strategies; distributed concurrency control and transactional guarantees across shards; multi region deployment strategies, cross region failover and disaster recovery; monitoring, capacity planning, automation for failover and backups, and cost optimization at scale. Candidates should be able to pick scaling approaches based on read and write patterns and explain operational complexity and trade offs introduced by distributed data.

MediumSystem Design

44 practiced

System design: Design an architecture to serve product detail reads for a large e-commerce site expecting 100k reads/sec and 2k writes/sec across 3 regions. Describe database choices, replication strategy, caching, read/write splitting, consistency model, and how you will handle search or filtering on product attributes.

EasyTechnical

36 practiced

You have a transactions table with schema transactions(transaction_id PK, user_id, amount DECIMAL, occurred_at TIMESTAMP, merchant_id INT). Reads are mostly per-user recent history, writes are frequent for multiple users. Propose a shard key and justify it with expected read/write patterns, cross-shard transaction considerations, and how you would handle rebalancing later.

HardSystem Design

32 practiced

Design question: Describe a global leader election mechanism for a distributed database control plane across multiple data centers using consensus protocols like Raft or Paxos. Explain quorum placement, leader stickiness, split-brain prevention and how you limit failover blast radius.

MediumTechnical

38 practiced

Problem solving: You observe a hot partition caused by a small set of keys receiving most writes, causing high latency and contention. Propose concrete mitigation techniques such as key redesign, write batching, app-level sharding, partition splitting, or using a different storage primitive. Explain operational impact of each option.

EasyTechnical

47 practiced

Explain leader-follower replication topology for relational databases. Describe the responsibilities of the leader and followers, how read replicas are used to scale reads, how replica lag arises and its effects on consistency, and common automatic and manual failover strategies.

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