Question 1

Explain database indexing and B-trees

Accepted Answer

**Target Audience:** Beginners to databases — you know what a table and a row are; no data-structures background needed beyond "sorted lists are easy to search".
**Difficulty:** Medium
**Verified with:** Node 22.22, Python 3.12, Go 1.24 and Java 21 (all four print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Behaviour shown comes from running the exa

Question 2

What indexing strategies improve database performance?

Accepted Answer

**Target Audience:** Developers who know what an index is and want to choose good ones. If "B-tree", "page" and "leaf" are new, read [Explain database indexing and B-trees](/interview-question/database-indexing-btrees) first; this page does not re-explain the tree.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output), plus real query plans from SQLite 3.45.1 via Python.

> **How to read this doc:** Every idea is explained in plain language first, the

Question 3

How would you design Nearby Friends?

Accepted Answer

**Target Audience:** Developers preparing for system design interviews. You know what a cache and a WebSocket are; the geo indexing side is covered on the sibling page about nearby drivers.
**Difficulty:** Hard
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. All behaviour shown comes from running

SYSTEM DESIGNDECODED.

Medium

Explain database indexing and B-trees

What indexing strategies improve database performance?

Hard

How would you design Nearby Friends?