Concepts/3. Data & Storage/B-Tree & B+Tree Indexing
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3. Data & StorageIntermediate

B-Tree & B+Tree Indexing

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Self-balancing search tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic O(log N) time.

STAFF ENGINEER TAKEAWAY: B+Trees store all table data pointers in leaf nodes linked horizontally, making range queries (BETWEEN x AND y) lightning fast.
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B+Tree Index Traversal Step

1
WHERE id = 42
Index lookup query
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2
Root Page Node
Evaluates ranges [1-50] vs [51-100]
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3
Internal Branch
Follows page pointer to [35-45]
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4
Leaf Node Page
Fetches exact row pointer from disk in 1 I/O
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✓ ARCHITECTURAL ADVANTAGES

Reduces disk page reads from millions to 3-4 I/O lookups.

✗ TRADE-OFFS & COMPLEXITIES

Every write requires page split balancing and index maintenance.

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Production Systems Leveraging This Pattern

⚡PostgreSQL B-Tree⚡MySQL InnoDB⚡SQLite
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More Topics in 3. Data & Storage

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🔺CAP Theorem (Consistency vs Availability)

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👯Database Replication (Leader-Follower)

A primary leader node accepts all write transactions and streams change logs to secondary read replicas to scale read QPS and enable high availability.