Exam Strategy and Cross-Domain Review

You made it — let’s tie it all together

Domain weight recap

Domain	Weight	Modules	Key Focus
D1: Design & Implement Data Models	35-40%	M1-M11	Partition keys, data modelling, SDK, queries, server-side
D2: Data Distribution	5-10%	M12-M14	Consistency levels, global replication, multi-region writes
D3: Integrate & Move Data	5-10%	M15-M17	Change feed, Synapse Link, data movement
D4: Optimize Performance	15-20%	M18-M21	Indexing, RU optimisation, integrated cache, materialized views
D5: Maintain Solution	25-30%	M22-M28	Monitoring, backup, security, cost, DevOps

Study time allocation:

• 60% on D1 + D5 (they’re 60-70% of the exam)
• 25% on D4 (performance optimisation is practical and code-heavy)
• 15% on D2 + D3 (important but lower weight)

Most-tested topics (the “golden list”)

These topics appear most frequently in exam questions. Know them cold:

Rank	Topic	Domain	Why It’s Tested
1	Consistency levels	D2	5 levels, trade-offs, per-request relaxation, 2× RU cost
2	Partition key design	D1	Even distribution, cross-partition queries, synthetic keys
3	Indexing policies	D4	Composite indexes, include/exclude, impact on writes
4	Change feed	D3/D4	Lease container, modes, materialized views, soft-delete
5	RU cost factors	D4	Point reads, consistency impact, query optimisation
6	Backup and restore	D5	Periodic vs continuous, restore to new account
7	Security (RBAC vs keys)	D5	Master keys danger, resource tokens, data plane roles
8	Throughput modes	D5	Serverless vs provisioned vs autoscale, limitations
9	Transactions	D1	Partition-scoped, batch operations, stored procedures
10	Global replication	D2	Failover priority, recovered region = read-only

Common exam traps

💡 Trap 1: 'Recovered region becomes writer again'

After automatic failover, the recovered region does NOT automatically become the write region. It returns as a read-only replica at the lowest priority. You must manually reprioritize. The exam loves this — Option A is almost always “it reclaims its role” and is almost always wrong.

💡 Trap 2: 'Strengthen consistency per-request'

You can only weaken (relax) consistency on a per-request basis. If the account default is Session, you CANNOT request Strong for a specific read. Direction: Strong → Bounded → Session → Prefix → Eventual.

💡 Trap 3: 'Serverless has unlimited throughput'

Serverless is NOT unlimited. It provides 5,000 RU/s per physical partition (total throughput scales with partition count), supports single region only, and has SLA only with availability zones. It can now be converted to provisioned throughput (NoSQL API).

💡 Trap 4: 'Restore always goes to a new account'

For periodic backup, restore always creates a new account (via Azure Support). For continuous backup, you can restore deleted containers/databases into the existing account or create a new account. In-place overwrite of data (not containers) does not exist — you choose between restoring to existing vs new account.

💡 Trap 5: 'Change feed captures deletes'

The default change feed (Latest Version) does NOT capture deletes. Use the soft-delete pattern (set a flag + TTL) or switch to All Versions and Deletes mode (preview — requires continuous backup, NoSQL API only).

Question-answering strategies

For “which consistency level” questions:

1. Does the scenario need read-your-own-writes? → Session
2. Does it need linearizable reads? → Strong (if single-write region)
3. Is cost the priority? → Eventual or Consistent Prefix
4. Are multi-region writes mentioned? → Eliminate Strong and Bounded

For “how to reduce RU cost” questions:

1. Can you use a point read instead of a query? → Always cheaper
2. Is the query cross-partition? → Add partition key filter
3. Is it SELECT *? → Project specific fields
4. Is the indexing policy default? → Optimise to include only queried paths

For “choose the throughput mode” questions:

1. Traffic is sporadic/dev-test? → Serverless
2. Traffic is predictable? → Provisioned manual (+ reserved capacity)
3. Traffic varies but somewhat predictable? → Autoscale
4. Need multi-region or SLA? → Eliminate serverless

The “if in doubt” rules:

• If in doubt on consistency: choose Session (it’s the default and most balanced)
• If in doubt on authentication: choose RBAC (recommended over keys)
• If in doubt on backup: choose Continuous (more granular, self-service)
• If in doubt on network security: choose Private Endpoints (most secure)

Final tips from the team

🚀 Priya (NovaSaaS): “Domain 1 is 35-40% of the exam. If you nail partition key design, data modelling, and the SDK, you’re already nearly halfway to passing. Don’t skimp on the fundamentals.”

🛒 Jake (GlobeCart): “Consistency levels were my nemesis. Make flashcards for all five levels — know the analogies, the RU costs, and which ones work with multi-region writes. I saw at least 6 consistency questions on my exam.”

📡 Amara (SensorFlow): “The change feed appears everywhere — not just in D3. Materialized views (D4), denormalization propagation (D1), and event-driven patterns (D4) all build on it. Understand the lease container and the soft-delete workaround deeply.”

⚙️ Marcus (FinSecure): “Domain 5 is 25-30% and it’s broad — security, monitoring, backup, cost, DevOps. The good news is most questions are scenario-based: ‘what should Marcus do when he sees 429 errors?’ Think about the operational response, not just the theory.”

Exam day checklist

• Review the golden list of most-tested topics
• Know all five consistency levels cold (analogies + technical details)
• Be comfortable reading C# SDK code for CRUD, queries, and change feed
• Understand CompareTable relationships (serverless vs provisioned, periodic vs continuous, etc.)
• Read each question twice — scenario questions hide the real question in the last sentence
• Eliminate obviously wrong answers first — then choose between the remaining
• Flag and return to questions you’re unsure about — don’t get stuck

🎬 Video walkthrough

🎬 Video coming soon

Exam Strategy — DP-420 Module 28

Exam Strategy — DP-420 Module 28

~14 min

Flashcards

Question

What are the two heaviest domains on the DP-420 exam?

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Answer

Domain 1: Design and Implement Data Models (35-40%) and Domain 5: Maintain an Azure Cosmos DB Solution (25-30%). Together they're 60-70% of the exam. Focus your study time accordingly.

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💡 Show hint

Question

What are the three 'if in doubt' defaults for the exam?

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Answer

1) Session consistency (default, most balanced). 2) RBAC with Entra ID (recommended over master keys). 3) Continuous backup (better granularity, self-service). When a question doesn't give enough detail to be specific, these are the safest answers.

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💡 Show hint

Question

What's the single most important thing to know for DP-420?

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Answer

Consistency levels — all five levels, their guarantees, their trade-offs (RU cost, latency, availability), per-request relaxation (weaken only), and which ones work with multi-region writes (Session, Consistent Prefix, Eventual). This topic alone can be 10-15% of the exam.

Click to flip back

💡 Show hint

Knowledge Check

Knowledge Check

A Cosmos DB account has multi-region writes enabled with Session consistency. A developer wants to perform a point read with Strong consistency for a critical financial check. What happens?

AThe read succeeds with Strong consistency at 2× RU costBThe read succeeds but silently uses Session consistency insteadCThe read fails — Strong consistency is not available with multi-region writes, and you cannot strengthen consistency per-requestDThe read fails because point reads don't support consistency overrides

Check Answer

Knowledge Check

A cross-partition query costs 500 RU per execution and runs 100 times per minute. Which optimisation would have the biggest impact?

AAdd a composite index for the ORDER BY clauseBRedesign the query to include the partition key in the WHERE clause (single-partition query)CEnable the integrated cache with 5-minute stalenessDSwitch from Session to Eventual consistency

Check Answer

Knowledge Check

Which of these is a common exam trap? (Select all that apply)

ARecovered regions automatically become the write region after failoverBYou can strengthen consistency on a per-request basisCServerless Cosmos DB supports multi-region writesDContinuous backup can restore deleted containers to the existing account

Check Answer

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🎉 Congratulations! You’ve completed all 28 modules of the DP-420 study guide. You’ve built a deep understanding of Azure Cosmos DB — from data modelling through global distribution, performance optimisation, and operational excellence.

Your next steps:

1. Review the golden list of most-tested topics
2. Re-do all flashcards and quizzes (aim for 90%+)
3. Take a practice exam under timed conditions
4. Schedule your exam — you’re ready!

Good luck from Priya, Jake, Amara, Marcus, and the entire team. 🚀🛒📡⚙️