Amazon QLDB vs CockroachDB: What are the differences?

Introduction

Amazon QLDB and CockroachDB are two popular databases used for different purposes. While QLDB is a fully managed ledger database service for creating auditable and transparent applications, CockroachDB is a distributed SQL database that offers high scalability and resilience.

Key Differences between Amazon QLDB and CockroachDB

1. Consistency Model: QLDB provides a strongly consistent model where all replicas of the data are updated before a write operation is considered successful. On the other hand, CockroachDB offers a slightly relaxed consistency model called "linearizable reads" which guarantees external consistency but allows for eventual inconsistencies during network partitions.

2. Data Replication: QLDB doesn't offer cross-region replication natively. It stores data within a single region and relies on the durability of Amazon S3 for data backups. In contrast, CockroachDB provides automatic and synchronous multi-region replication, allowing for improved availability and disaster recovery.

3. Transaction Support: QLDB supports ACID transactions with serializable isolation level, ensuring data integrity and consistency at all times. CockroachDB also supports ACID transactions but provides multiple isolation levels, including serializable, snapshot, repeatable read, and read committed.

4. Query Language: QLDB uses PartiQL, a SQL-compatible query language optimized for nested documents and closely integrated with QLDB's document model. While CockroachDB also supports SQL, it offers a more traditional SQL dialect with extensions for distributed transactions and scalability features.

5. Concurrency Control: QLDB uses an optimistic concurrency control mechanism, allowing multiple concurrent readers and writers with optimistic locking and conflict resolution. CockroachDB, on the other hand, utilizes distributed consensus algorithms and multi-version concurrency control (MVCC) to ensure consistency and isolation in a distributed environment.

6. Scalability and Sharding: CockroachDB is designed to scale horizontally across commodity hardware by automatically sharding data across multiple nodes. QLDB, being a managed service, abstracts the underlying infrastructure details and provides built-in scalability, but with limited control over the sharding process.

In Summary,

Amazon QLDB and CockroachDB differ in their consistency models, replication capabilities, transaction support, query languages, concurrency control mechanisms, and scalability approaches.