AI-200 Data Services: Cosmos DB, PostgreSQL, Redis, and Vector Search

Azure data services are the heaviest part of AI-200, and they deserve focused study. The exam is not only asking whether you know service names. It wants to know whether you can design retrieval, indexing, caching, and data-change workflows for AI applications.

Cosmos DB for NoSQL

Cosmos DB shows up in AI-200 as a NoSQL data store, but also as a retrieval component. Study SDK-based access, query design, request units, consistency levels, indexing policies, embeddings, vector similarity search, and change feed processing. A strong candidate can explain how a new document moves from storage to embedding to searchable retrieval.

Practice reading scenarios for cost and performance hints. If the problem mentions high RU consumption, inefficient filters, or slow retrieval, indexing policy and query shape may be the real issue. If the problem mentions reacting to new or updated items, the change feed processor should be on your list.

Azure Database for PostgreSQL and pgvector

PostgreSQL matters when relational metadata and vector retrieval belong together. You should know how to model tables, choose data types, store embeddings, create vector indexes, add metadata indexes, and use filters with similarity search. For AI-200, pgvector is not just an extension name. It is part of an application architecture.

Also study connection management. Serverless and containerized AI services can create connection pressure. Connection pooling, limits, and secure driver configuration are practical exam topics.

Azure Managed Redis

Redis can support caching, expiration, invalidation, and vector indexing. That means it can reduce latency for repeated retrieval and store short-lived conversation context. Know when cache invalidation matters: a stale grounding snippet can produce a bad answer even if the rest of the architecture is correct.

Use the ExamStudyApp AI-200 practice exam to separate real understanding from recognition. If you can explain why Cosmos DB, PostgreSQL, or Redis fits a scenario, you are much closer to exam-ready than someone who only memorized the product list.