CockroachDB vs TiDB: What are the differences?

Introduction

CockroachDB and TiDB are both distributed SQL databases designed for high availability, scalability, and fault-tolerance. However, there are several key differences between the two:

1. Consistency model: CockroachDB follows a strong consistency model, ensuring that all reads see the most recent write. On the other hand, TiDB follows a hybrid consistency model, offering both strong and eventual consistency. This means that while CockroachDB provides strict consistency, TiDB allows for more flexibility in trading off consistency for latency in some scenarios.

2. Architecture: CockroachDB is based on a hierarchical structure, where data is divided into zones, ranges, and replicas. It utilizes a consensus protocol called Raft to handle leader elections and ensure replication. In contrast, TiDB adopts a distributed architecture inspired by Google's Spanner, using a distributed transaction protocol called Multi-Raft to achieve strong consistency across multiple regions.

3. SQL compatibility: CockroachDB aims to provide full compatibility with the PostgreSQL SQL dialect, including support for advanced features like indexing and JOINs. On the other hand, TiDB is compatible with the MySQL ecosystem, supporting common SQL syntax and many of the associated tools and libraries.

4. Storage engine: CockroachDB uses its own storage engine called Pebble, optimized for distributed use cases. It provides transactional key-value storage and offers additional features like range splitting and distributed snapshots. In contrast, TiDB relies on TiKV as its storage engine, which is a distributed Key-Value store based on the Raft protocol.

5. Tooling and ecosystem: CockroachDB has a more mature and feature-complete tooling ecosystem, including a web-based admin UI, built-in backup and restore functionality, along with integration with popular observability tools like Prometheus and Grafana. While TiDB also provides some tooling like TiDB Dashboard, the ecosystem is still evolving and may not offer the same level of features and integration.

6. Performance considerations: CockroachDB has a higher write latency compared to TiDB, as it prioritizes strong consistency by default. TiDB, on the other hand, can achieve lower latency for writes by relaxing consistency guarantees when necessary. Additionally, CockroachDB's architecture allows it to scale horizontally better, while TiDB may be limited by the performance of its storage engine.

In summary, CockroachDB and TiDB differ in their consistency models, architecture, SQL compatibility, storage engines, tooling ecosystems, and performance considerations. These differences allow users to choose the database that best fits their specific requirements and use cases.