Synapse: a microservices architecture for heterogeneous-database web applications

The growing demand for data-driven features in today's Web applications -- such as targeting, recommendations, or predictions -- has transformed those applications into complex conglomerates of services operating on each others' data without a coherent, manageable architecture. We present Synapse, an easy-to-use, strong-semantic system for large-scale, data-driven Web service integration. Synapse lets independent services cleanly share data with each other in an isolated and scalable way. The services run on top of their own databases, whose layouts and engines can be completely different, and incorporate read-only views of each others' shared data. Synapse synchronizes these views in real-time using a new scalable, consistent replication mechanism that leverages the high-level data models in popular MVC-based Web applications to replicate data across heterogeneous databases. We have developed Synapse on top of the popular Web framework Ruby-on-Rails. It supports data replication among a wide variety of SQL and NoSQL databases, including MySQL, Oracle, PostgreSQL, MongoDB, Cassandra, Neo4j, and Elasticsearch. We and others have built over a dozen microservices using Synapse with great ease, some of which are running in production with over 450,000 users.