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.

HardTechnical

43 practiced

Explain how snapshot isolation (SI) can be implemented across shards and what is required to provide serializability across distributed partitions. Discuss MVCC, timestamp allocation (logical or physical), global ordering mechanisms (e.g., TrueTime or hybrid logical clocks), and the performance vs correctness trade-offs for each approach.

EasyTechnical

48 practiced

Explain ACID properties (atomicity, consistency, isolation, durability) and contrast them with BASE/eventual consistency models. As a backend developer, give clear examples of when you would prefer strong ACID guarantees versus eventual consistency and list application-level patterns to cope with eventual consistency.

EasyTechnical

41 practiced

Explain the differences between vertical (scale-up) and horizontal (scale-out) database scaling. In the context of a backend developer responsible for a mid-size e-commerce platform that currently runs a single PostgreSQL instance, describe when you'd prefer each approach, the practical limits, cost implications, operational complexity, and how they affect availability and fault tolerance.

MediumTechnical

42 practiced

A PostgreSQL cluster is experiencing high connection counts and slow queries under peak load. As the backend developer, propose a remediation plan that includes connection pooling (pgbouncer), ORM-level changes, query plan analysis, index strategies, and migration steps to reduce latency and connection saturation without impacting correctness.

HardTechnical

42 practiced

Describe a time (or a realistic hypothetical scenario) where you had to choose between availability and data correctness during a production outage. As a backend developer or team lead, explain how you evaluated the trade-offs, communicated with stakeholders, executed the decision, and what post-mortem actions you took to prevent recurrence. Use STAR (Situation, Task, Action, Result) structure.

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