Intermediate~3h
Indexes & Access Patterns in SQL & DatabasesInterview Readiness Check
B-tree internals, composite index left-prefix rule, covering indexes, functional indexes, write overhead.
b-treeindexcomposite indexcovering indexpartial indexfunctional indexseq scan
Learning path
Try a sample question
A PostgreSQL users table has 10M rows. A query WHERE email = 'user@example.com' takes 8 seconds without an index and 2ms after CREATE INDEX ON users(email). Why does the index help so dramatically?
A.The index stores a compressed copy of the table, reducing disk reads
B.Indexes reorder the rows physically on disk to match the query's access pattern
C.The index caches the query result in memory so subsequent calls skip disk entirely
D.A B-tree index enables binary search O(log n) directly to the matching rows; without it the database must sequentially scan all 10M rows O(n)
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What this module tests
- Conceptual understanding of indexes & access patterns fundamentals
- Trade-offs and design decisions in real system scenarios
- b-tree and index — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the Indexes & Access Patterns check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the Indexes & Access Patterns check test?
- The check covers b-tree internals, composite index left-prefix rule, covering indexes, functional indexes, write overhead. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Indexes & Access Patterns?
- Key concepts include: b-tree, index, composite index, covering index, partial index, functional index, seq scan. These frequently appear in sql & databases interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study Indexes & Access Patterns?
- Most engineers spend around 3 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before Indexes & Access Patterns?
- Indexes & Access Patterns builds on Schema Design & Normalization. Complete those first for the best results.
- Is b-tree, index, composite index covered?
- Yes. The Indexes & Access Patterns module covers b-tree, index, composite index among other key concepts. The check includes questions that reflect real sql & databases interview patterns.