CockroachDB Interview Questions and Answers for 10 years experience

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100 CockroachDB Interview Questions & Answers (10+ Years Experience)

  1. What are the core architectural principles behind CockroachDB?

    • Answer: CockroachDB is built upon several key architectural principles: distributed SQL database, horizontally scalable, fault-tolerant, geo-replicated, and ACID compliant. It leverages a distributed consensus algorithm (Raft) for data consistency and uses a multi-tenant architecture to maximize resource utilization. Its design emphasizes high availability and resilience even with node failures or network partitions.

  2. Explain the concept of "global secondary indexes" in CockroachDB. What are the trade-offs involved in using them?

    • Answer: Global secondary indexes (GSIs) in CockroachDB allow querying data based on non-primary key columns, similar to indexes in traditional databases. However, unlike local indexes, GSIs are distributed across the entire cluster, improving query performance on large datasets. The trade-offs include increased write latency due to the need to update multiple indexes, and increased storage consumption. Choosing the right indexes needs careful consideration of the query patterns and data size.

  3. How does CockroachDB handle schema changes? Describe the process and potential implications.

    • Answer: Schema changes in CockroachDB involve using SQL statements like `ALTER TABLE`. The system handles these changes in a distributed manner, ensuring consistency across the cluster. The process involves a rolling update of the schema across all nodes. Potential implications include temporary performance degradation during the schema change, and potential downtime if the change is complex or poorly managed. Backups are strongly recommended before major schema alterations.

  4. Discuss the different consistency levels available in CockroachDB and their implications for application design.

    • Answer: CockroachDB offers different consistency levels, primarily `SERIALIZABLE` and `CONSISTENT`. `SERIALIZABLE` ensures strict serializability, guaranteeing that transactions appear to execute one after another. This is crucial for applications requiring strict data integrity. `CONSISTENT` offers a weaker guarantee, ensuring that reads see a consistent snapshot of the data, but the order of transactions might not be strictly sequential. Application design should choose the consistency level that best matches the data integrity requirements, balancing consistency with performance.

  5. Explain how CockroachDB manages transactions and ensures ACID properties in a distributed environment.

    • Answer: CockroachDB utilizes a distributed consensus algorithm (Raft) to guarantee ACID properties (Atomicity, Consistency, Isolation, Durability) in a distributed environment. Transactions are managed across multiple nodes, ensuring that either all changes are committed or none are. The Raft consensus protocol ensures that all nodes agree on the order of operations and commit changes consistently, even in the presence of network partitions or node failures. Two-phase commit (2PC) is employed to ensure atomicity across multiple nodes.

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