Google Cloud Spanner and Google Cloud SQL are both managed database services offered by Google Cloud Platform, but they have some fundamental differences. Here are the main distinctions between the two:
- Database Type: Google Cloud Spanner is a globally distributed, horizontally scalable, and strongly consistent relational database. It is designed to handle large-scale, mission-critical transactional workloads with low latency. Cloud SQL, on the other hand, is a fully managed relational database service that supports MySQL, PostgreSQL, and SQL Server. It provides a traditional relational database experience.
- Scalability: Cloud Spanner is specifically built to scale horizontally across multiple regions and continents. It uses a distributed architecture and automatically shards data across various nodes, allowing it to handle massive amounts of data and high throughput requirements. Cloud SQL offers vertical scalability, meaning you can increase the computing resources (CPU, RAM) allocated to your instance, but it does not natively support horizontal scaling across multiple regions.
- Consistency: Cloud Spanner provides strong consistency, meaning that when a write operation is committed, it is immediately visible to all subsequent read operations globally. Cloud SQL offers transactional consistency within a single database instance, but it doesn't provide the same global consistency guarantees as Cloud Spanner.
- Global Replication: Cloud Spanner allows you to replicate your data globally across multiple regions, providing low-latency access to your data from anywhere in the world. This enables disaster recovery, data locality, and the ability to serve users in different geographic locations with minimal latency. Cloud SQL offers regional replication, allowing you to replicate your data within a specific region for improved availability and durability.
- Data Model: Both services support relational data models, but Cloud Spanner provides additional features such as secondary indexes, foreign keys, and SQL support for complex querying. Cloud SQL supports the features and functionalities provided by the underlying relational database engines, such as MySQL or PostgreSQL.
- Managed Service: Both Cloud Spanner and Cloud SQL are fully managed services, which means Google takes care of infrastructure management, backups, security patches, and software updates. You can focus on developing applications without worrying about server maintenance. However, Cloud Spanner's underlying infrastructure is more complex due to its distributed nature.
In summary, Cloud Spanner is designed for globally distributed, highly scalable, and strongly consistent transactional workloads, while Cloud SQL provides a traditional relational database experience with vertical scalability and regional replication. The choice between the two depends on your specific requirements, such as scalability needs, global consistency, and the type of database engine (MySQL, PostgreSQL, or SQL Server) you prefer to use.