SQL & NoSQL Database Solutions

DynamoDB's single-table design is an architectural pattern where all entity types (users, orders, products, sessions) are stored in a single DynamoDB table differentiated by their primary key prefix and sort key structure. The rationale: DynamoDB is optimised for single key-value lookups and range queries on the sort key; joins across tables require two separate reads at the application level. By placing all related entities in the same table with carefully designed sort key structures, you can retrieve a user and all their orders in a single table query. The controversy: single-table design requires knowing all access patterns at design time (it is very difficult to add new access patterns post-launch without a full reindex), it is counterintuitive to relational database thinking (requires a mental model shift), and it makes the data harder to inspect and debug. ClickMasters uses single-table design for DynamoDB when the access patterns are well-defined and stable, and recommends PostgreSQL when access patterns are exploratory or likely to evolve.

Polyglot persistence is the architectural approach of using multiple database technologies each selected based on the specific requirements of the data it stores. A typical polyglot stack for a B2B SaaS product: PostgreSQL for transactional data (user accounts, billing, application state), Redis for caching and queues (hot data, session tokens, background job queues), Elasticsearch for search (indexed from PostgreSQL via CDC users search products, support agents search tickets), and ClickHouse for analytics (event data from Kafka, aggregations that would be too expensive in PostgreSQL). The benefit: each database is used for what it does best. The cost: operational complexity (multiple database technologies to monitor, back up, scale, and update), data synchronisation (changes in the primary database must propagate to derived databases CDC pipelines, consistency delays), and developer expertise (the team needs proficiency in multiple database technologies). Polyglot persistence pays off at scale; for smaller teams and products, PostgreSQL with Redis is sufficient for the majority of use cases.