DP-203 Design and implement data storage Practice Question
You need to design a storage solution for IoT device telemetry data that will be queried by time range. The data is append-only and arrives at high velocity. Which TWO features should you use to optimize query performance and reduce costs?
⚠ Common exam trap
Candidates often confuse indexing (B) with partitioning, but for append-only analytical workloads, indexes add write overhead and cost without benefit, while date partitioning directly enables partition elimination for time-range queries.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Store data in columnar format (e.g., Parquet)
Columnar formats like Parquet store data by column rather than by row, which significantly reduces I/O when querying only a subset of columns (common in time-range queries). This compression and column pruning directly lowers storage costs and speeds up scan-heavy analytical queries on append-only IoT telemetry data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Store data in columnar format (e.g., Parquet)
Why this is correct
Columnar format reduces I/O and improves compression.
- ✗
Create indexes on all columns
Why it's wrong here
Indexing all columns increases write cost and storage.
- ✗
Enable row-level security
Why it's wrong here
Row-level security is for access control, not performance.
- ✓
Partition the data by date
Why this is correct
Time-based partitioning allows query pruning.
- ✗
Enable geo-redundant storage
Why it's wrong here
Geo-redundancy increases cost and does not improve query performance.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DP-203 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DP-203 exam.