DP-420 case studies
DP-420 · Put your knowledge to work in context.
The Microsoft Certified: Azure Cosmos DB AI Developer Associate is an intermediate-level Microsoft certification for developers who build and optimize applications on Azure Cosmos DB. Microsoft positions the role around cost-effective, high-performance, scalable applications that use Cosmos DB as the system of record for agent memory, conversation state, retrieval indexes, grounding data, and application data. The DP-420 case studies are 5 cases and about 5,212 words.
1Hot Tenant on a Shared Shipments Container
Northwind Freight runs a multi-tenant SaaS on Azure Cosmos DB for NoSQL. All tenants share one container, shipments , with partition key /tenantId and 120,000 RU/s provisioned manually.
917 words, about 5 min2Ledger Consistency and Key Custody for a Regulated Bank
A European bank runs its ledger on Azure Cosmos DB for NoSQL with the write region in West Europe and read regions in North Europe and East US. Auditors require that any read issued after a write is acknowledged returns that write or a newer one, and that a write is never acknowledged before it is committed in a majority of replicas in the write region.
1,122 words, about 6 min3Telemetry Container That Writes Too Expensive and Reads Too Much
A telemetry platform stores 4 KB JSON documents in a 6 TB Cosmos DB for NoSQL container with the default indexing policy; ingestion peaks at 8,000 documents per second and each write costs about 22 RU. Three problems dominate the support queue: (1) SELECT FROM c WHERE c.deviceId = @d AND c.type = 'alert' ORDER BY c.recordedAt DESC fails with 'The index path corresponding to the specified order-by item is excluded or invalid'; (2) SELECT FROM c WHERE LOWER(c.region) = 'emea' AND c.recordedAt @t reads 40 GB of index per execution; (3) the product team wants a count of alerts per device per day, executed each time a dashboard loads.
978 words, about 5 min4Retrieval Quality and RU Budget for a Ticket Assistant
A support-desk assistant stores 2.2 million ticket chunks (about 1.5 KB each, with 1536-dimension embeddings from Azure OpenAI) in a Cosmos DB for NoSQL container partitioned by /tenantId with 30,000 RU/s. Retrieval must return the top 5 nearest chunks filtered to the caller's tenant, at p95 under 150 ms and under 20 RU per query.
1,090 words, about 5 min5Order Service Under Flash-Sale Load and Two Writers
A retail order service writes orders and up to 40 line items per order to a Cosmos DB for NoSQL container partitioned by /customerId , using the .NET SDK. Throughput is 100,000 RU/s provisioned manually; during a 20-minute flash sale the account sustains 95% utilization and throttles, then drops to about 4% for the remaining 23 hours.
1,105 words, about 6 min