Model and partition
Choose consistency levels and throughput, design partition keys and hierarchical keys, and decide when to embed or reference data.






























DP-420 is an Associate exam for developers who build on Azure Cosmos DB, including agent memory and retrieval indexes. Data modeling, partitioning and the change feed lead, then security, performance, and vector and hybrid search for RAG and memory. Since 6 October 2026 it is the Azure Cosmos DB AI Developer Associate, with a rewritten outline and a new exam title.
Choose consistency levels and throughput, design partition keys and hierarchical keys, and decide when to embed or reference data.
Write queries, point reads, patches and transactional batches, and react to changes with the change feed.
Set up authentication, network security and multi-region failover, and tune queries and indexes against latency targets.
Build vector, full-text and hybrid search for RAG, design agent memory stores, and mirror data into Microsoft Fabric.
We design this course ourselves. Microsoft runs the exam and issues the credential, and LUNARTECH is independent of Microsoft.
Every design decision sits on the account, database and container model. You choose an API, understand throughput as request units, and pick capacity modes that fit steady, spiky and unknown workloads.
You build A capacity estimate for a workload, comparing provisioned, autoscale and serverless.
Distributed data forces a choice between freshness, speed and availability. You learn the consistency levels, what each promises a reader, and how to set and override them per request.
You build A consistency recommendation for three scenarios, each justified by its read and write behavior.
Cosmos DB rewards models built around access patterns. You decide when to embed related data and when to reference it, denormalize for reads, and keep copies in step.
You build A data model for a conversational application, with its access patterns written down.
The partition key decides scale, cost and the queries you can afford. You choose keys that spread load, use hierarchical partition keys, and recognize hot partitions and cross-partition queries before they hurt.
You build A partition key design tested with generated data and checked for skew.
Efficient operations are the difference between a cheap workload and an expensive one. You write queries, prefer point reads, patch items in place, and group writes in transactional batches and bulk operations.
You build A data access layer with point reads, patches and batch writes that handles throttling.
The change feed turns a database into an event source. You read it with the SDK and with Azure Functions, handle ordering, and design downstream views, search indexes and notifications.
You build A change feed processor that keeps a second container in step with a source container.
A database account is a high-value target. You replace keys with Entra identities and data-plane roles, restrict network paths, and protect data with encryption options.
You build A Cosmos DB account with key access disabled, identity-based roles and private networking.
Cosmos DB can span regions, but only if you design for it. You configure replication and failover, choose backup modes, and plan restores for the failures that actually occur.
You build A two-region account with a rehearsed failover and a point-in-time restore.
Query cost is visible if you know where to look. You read query metrics and request charges, tune indexing policies, and use caching and design changes to reach latency targets.
You build A tuning report that lowers the request charge of three queries, with the policy changes behind it.
Production estates have many accounts and teams. You apply governance, monitoring and cost controls across accounts, and keep configuration consistent as the fleet grows.
You build An infrastructure-as-code template for a standard account, with monitoring and policy applied.
Retrieval is where AI applications meet the database. You store embeddings, build vector and full-text indexes, combine them in hybrid queries, and use the results to ground a language model.
You build A RAG back end on Cosmos DB with vector and hybrid retrieval, measured against test questions.
Agents that remember are more useful, and memory is a data problem. You design stores for short-term and long-term memory, keep them scoped per user and per agent, and retrieve what matters.
You build A memory store for an agent that scopes, expires and retrieves memory per user.
Analytics should not slow transactions. You mirror Cosmos DB data into Microsoft Fabric, query it for reporting, and decide what to mirror and what to keep out.
You build A mirrored container queried from Fabric for a business report.
Build one data layer for an AI application. You model and partition the data, secure and replicate it, add retrieval and memory, and prove it meets latency and cost targets.
You build A Cosmos DB back end with retrieval, agent memory, analytics and measured latency and cost.

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No single job owns it. Here’s where each role leans hardest, and where its work ends up.
A weak partition key caps your scale. Fix it before the data grows.
Design, Secure and tune
AI applications, SaaS companies, Retail and e-commerce
Agent memory has to survive a restart. A durable store keeps conversation state.
AI and analytics
AI applications, Financial services
Mirroring puts operational data in Fabric. Analysts query it without touching the app.
AI and analytics, Design
Retail and e-commerce, Healthcare
The partition key you pick sets cost and scale for years. Data modeling is the decision that is hardest to change.
Design, Secure and tune
SaaS companies, Financial services
Retrieval quality depends on how vectors are stored. Hybrid search blends vectors with keyword matches.
AI and analytics
AI applications, Retail and e-commerce
A globally replicated database must stay up and fast. Availability and throughput tuning are part of the job.
Secure and tune
Financial services, Healthcare
Agents need memory that outlives a single chat. You choose where it lives and how it is searched.
Design, AI and analytics
SaaS companies, AI applications
A weak partition key caps your scale. Fix it before the data grows.
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100 minutes, proctored, pearson vue, in English and 9 other languages. The passing score is 700 of 1000.
Microsoft expects experience developing applications in C# or Python, and familiarity with Azure services, generative AI concepts, retrieval-based systems and application development practices.
1 year. Pass a free online assessment on Microsoft Learn.
Yes. On 6 October 2026 Microsoft renamed it Azure Cosmos DB AI Developer Associate, and the exam is now titled Building AI Applications with Azure Cosmos DB.
We last reviewed it on 5 November 2026, from Microsoft’s own pages. Details change, so check the official page before you book.
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Prove you can build AI applications on Azure Cosmos DB. Start with a free trial, or enroll in a plan and work through the course at your own pace. Microsoft runs the exam and issues the credential.
LUNARTECH is independent of the vendors and certifying bodies listed here. Their names, exam titles and marks belong to them, exams are run by them, and credentials are issued by them. Reviewed 5 November 2026. Catalogues change often, so confirm the details on the official page before you book.