Microsoft Certified: Azure Cosmos DB Developer Specialty (DP‑420) Practice Exams
About the Azure DP-420 exam
Exam at a glance
Microsoft's deepest certification on a single data platform — Azure Cosmos DB — sitting at the specialty tier.
Who this exam is for
DP-420 is the strongest fit for software engineers and solution architects designing NoSQL-backed applications with global distribution, low-latency, and elastic-scale requirements. If you're building production apps on Cosmos DB — modeling data, picking partition keys, tuning RU/s, choosing a consistency level — this certification validates those exact decisions.
Skill domains
- Design and implement data models — ~35–40%
- Design and implement data distribution — ~5–10%
- Integrate an Azure Cosmos DB solution — ~5–10%
- Optimize an Azure Cosmos DB solution — ~15–20%
- Maintain an Azure Cosmos DB solution — ~25–30%
Prerequisites
No formal prerequisites. Microsoft recommends professional development experience plus hands-on familiarity with at least one Azure Cosmos DB API. The NoSQL API is the primary focus on the exam, but MongoDB, Cassandra, Gremlin, and Table APIs are also tested. You should be comfortable reading C# or Java code, writing SQL-style queries for the NoSQL API, working with PowerShell, and interpreting JSON. AZ-204 (Azure Developer) or DP-900 (Data Fundamentals) are common warm-up certs but not required.
Why take this certification
- The deepest Cosmos DB credential Microsoft offers. No other Microsoft certification spends 100 minutes drilling on a single data platform. If Cosmos DB sits in your stack, DP-420 is the credential that proves you understand it end-to-end.
- Highly portable skill set. Globally distributed, multi-API NoSQL is a category — patterns learned here transfer to DynamoDB, MongoDB Atlas, and Cassandra on other clouds.
- Free annual renewal. Microsoft's renewal assessment on Microsoft Learn is free and shorter than the original exam — you keep the credential current without paying $165 every year.
- Practical scope. The skills outline maps directly to what production Cosmos DB teams actually do: partition design, RU/s capacity, change feed, indexing policies, multi-region writes, point-in-time restore.
What you'll learn in the DP-420 exam
DP-420 validates that you can design, build, and operate Cosmos DB solutions that scale globally without falling off the consistency, cost, or latency cliff. Most questions describe a workload with specific constraints (throughput target, geographic spread, consistency need) and ask which combination of Cosmos DB features fits.
Data modeling for NoSQL
- Denormalization vs referencing — when to embed related entities in a single document vs split across documents with foreign-key-style references.
- Hierarchical partition keys — multi-level partition keys (e.g.
/tenantId/userId) and when they beat single-level keys. - Change feed processing — the change feed processor library, Azure Functions triggers, lease containers, and idempotency patterns.
- Document size, TTL, and unique keys — schema-on-read design without losing data integrity.
Partition key design + capacity planning
- RU/s mechanics, the cost of point reads vs queries vs writes, and how indexing affects RU consumption.
- Choosing between provisioned, autoscale, and serverless throughput modes by traffic shape.
- Avoiding hot partitions, planning for storage limits per logical partition (20 GB), and shard-key cardinality.
Consistency levels
- The five consistency levels — strong, bounded staleness, session, consistent prefix, eventual — and the latency, availability, and RU cost trade-offs of each.
- Per-request consistency relaxation, default account consistency, and multi-region implications.
Global distribution
- Multi-region writes, conflict resolution policies (last-write-wins, custom resolver via stored procedure).
- Automatic vs manual failover, write region selection, and read priority configuration.
- Latency expectations across regions and how consistency level affects multi-region performance.
Integration
- Synapse Link — analytical store, near-real-time analytics without ETL.
- Azure Functions triggers, change feed processor library, Stream Analytics inputs/outputs.
- SDK choice across languages (.NET, Java, Python, Node.js) and the Cosmos DB Emulator for local dev.
Optimization + monitoring
- Query tuning, indexing policy customization (include/exclude paths, composite indexes, spatial indexes).
- Cross-partition queries vs point reads, server-side programming (stored procedures, triggers, UDFs).
- Azure Monitor, diagnostic logs, request metrics, and tracking RU/s consumption per operation.
Resilience
- Continuous backup with point-in-time restore (7-day or 30-day windows).
- Multi-region replication for disaster recovery, automatic failover RPO/RTO characteristics.
How the practice exams help
Each free question and every premium exam mirrors Microsoft's scenario format — a constrained workload, several plausible Cosmos DB configurations, one or more that fit best. Detailed explanations cover not just why the right answer is right but why the others are wrong, so you internalize the trade-offs.
How to prepare for the DP-420 exam
A successful DP-420 preparation strategy combines theoretical study, hands-on Cosmos DB practice, and exam simulation. Recommended approach:
- Study the Cosmos DB platform (4–5 weeks). Walk the official Microsoft Learn DP-420 learning path end-to-end. Pay special attention to partition key design, RU/s mechanics, and the five consistency levels — these concepts thread through every exam domain.
- Hands-on Cosmos DB (3–4 weeks). Spin up the Cosmos DB free tier (1000 RU/s + 25 GB free forever) and build real workloads. Practice partition key experiments, indexing policy edits, RU/s tuning, change feed consumers, and multi-region write configurations. Use the Cosmos DB Emulator for offline development without burning RU/s.
- Read the official docs (1–2 weeks). Microsoft's Azure Cosmos DB documentation is the source of truth for every fact on the exam. Focus on the NoSQL API conceptual guides, the request unit deep dive, and the consistency-level guide.
- Practice exams (1–2 weeks). Take timed practice tests to surface weak spots. Detailed answer explanations matter more than score percentage at this stage — you're trying to internalize trade-offs, not memorize. Aim for consistent 80%+ on practice questions before booking the proctored exam.
Recommended timeline
10–14 weeks of focused study (10–15 hours per week) for developers with at least some Azure experience. If you already hold AZ-204, you can compress the Azure-platform portions and focus on Cosmos DB specifics — closer to 8–10 weeks.
Official resources
Bookmark the official DP-420 certification page for the skills outline and the DP-420 study guide for the topic checklist. Microsoft also offers a free DP-420 practice assessment on Microsoft Learn — use it for question-style familiarization, not for raw question volume.
Frequently asked questions
Are these actual exam questions?
No. All Nex Arc Azure DP-420 practice questions are original content based on the provider's published exam blueprint, official documentation, and real-world scenarios across every topic the exam covers. We do not offer brain dumps, leaked questions, or actual exam content. Using or distributing real exam questions violates certification provider agreements and can result in certification revocation.
How many questions are in the Azure DP-420 exam?
Microsoft does not publish an exact question count for DP-420. Most candidates report between 40 and 60 questions delivered in 100 minutes. Question formats include multiple choice, multiple response, drag-and-drop, case studies, and short scenarios. The exam may also include interactive labs depending on the version you receive.
What's the DP-420 passing score?
The passing score is 700 out of 1000. Microsoft uses a scaled scoring model, so not every question carries the same weight. Case studies and labs typically contribute more points than standalone multiple-choice items. Focus on understanding Azure Cosmos DB design trade-offs rather than memorizing answers.
How do I access the full DP-420 practice exam?
Click on the Buy Now button in the sidebar to purchase the complete Azure DP-420 course. After payment, you'll have instant access to 12 practice exams with detailed explanations and lifetime access.
What are the prerequisites for the DP-420 exam?
There are no formal prerequisites for DP-420, but Microsoft strongly recommends professional development experience and hands-on familiarity with at least one Azure Cosmos DB API. The NoSQL API is the primary focus, though MongoDB, Cassandra, Gremlin, and Table APIs are also tested. You should be comfortable reading C# or Java code, writing SQL-style queries for the NoSQL API, working with PowerShell, and interpreting JSON. Candidates often hold AZ-204 (Azure Developer Associate) or DP-900 (Azure Data Fundamentals) before attempting DP-420.
How long is the DP-420 certification valid?
Microsoft certifications, including DP-420, are valid for one year. Microsoft offers a free annual renewal assessment on Microsoft Learn — you do not need to retake the full proctored exam to stay certified. The renewal opens six months before your certification expires and is shorter and easier than the original exam, focusing on what has changed in the technology. If you let your certification expire, you must retake the full DP-420 exam at the standard price.
What's the exam cost and can I retake it if I fail?
DP-420 costs $165 USD in the United States (Microsoft Specialty pricing), with regional pricing in other countries. The exam is delivered through Pearson VUE at testing centers or via online proctoring. If you fail your first attempt, you must wait 24 hours before retaking. For subsequent retakes, the waiting period increases (typically 14 days). You may take the exam a maximum of five times within a 12-month period. Microsoft's Exam Replay offer occasionally bundles one retake at a discount — check the official certification page before booking.
What Azure Cosmos DB features are most heavily tested on DP-420?
Based on Microsoft's skills outline, the most heavily tested areas are: partition key design and hierarchical partition keys, request unit (RU/s) capacity planning (provisioned vs autoscale vs serverless), the five consistency levels (strong, bounded staleness, session, consistent prefix, eventual), global distribution and multi-region writes, change feed processing (change feed processor library, Azure Functions triggers), indexing policy customization, optimizing point reads versus cross-partition queries, Synapse Link analytical store, and continuous backup with point-in-time restore. The NoSQL API is the primary focus, but expect a small number of questions on the MongoDB, Cassandra, Gremlin, and Table APIs.
Which Cosmos DB API does DP-420 focus on?
DP-420 focuses primarily on the Azure Cosmos DB for NoSQL API (formerly the SQL API or Core API), but the other supported APIs — MongoDB, Cassandra, Gremlin (graph), and Table — are also in scope. Most exam questions assume the NoSQL API; questions about the other APIs are typically scenario-based ("a customer is migrating from MongoDB Atlas, which API should they choose?"). You should know each API's primary use case, which Cosmos DB features each one supports, and the SDK languages available for each.
Can I retake the DP-420 exam if I fail?
Yes. You can retake DP-420 24 hours after your first failed attempt. For the third through fifth attempts, the waiting period extends to 14 days between attempts. You may take the exam a maximum of five times in a 12-month period. Each attempt requires a new $165 payment unless you purchased an Exam Replay bundle.