Pagination: Offset vs Cursor-Based
Offset
Page + limit style
- - Simple mental model
- - Degrades on large offsets
Cursor
Token-based traversal
- - Stable under inserts
- - More complex client logic
Consistency
Avoid duplicates/gaps
- - Stable sort key required
- - Handle stale cursors
UX
Infinite scroll vs pages
- - Context retention
- - Back-navigation strategy
Core Lens
Use offset for simple stable lists; use cursor when data mutates frequently or scale grows.
Flow
Choosing the right pagination strategy for performance, consistency, and UX in real frontend systems.
Rule of thumb: Use offset for stable, page-number UIs. Use cursor for feeds and infinite scroll with frequent inserts/deletes.
Offset-Based Pagination
Offset asks the server for items starting at a numeric position.
GET /api/posts?page=3&limit=20
GET /api/posts?offset=40&limit=20Advantages
- Simple and fast to implement
- Easy “Go to page N” support
- Usually returns total pages/count
- Good for admin tables and static lists
Disadvantages
- Deep offsets can be slower at scale
- Records may shift when new data is inserted
- Can show duplicates or skip items in live feeds
Cursor-Based Pagination
Cursor uses a pointer from the last item in the current result set.
GET /api/posts?limit=20
GET /api/posts?cursor=eyJjcmVhdGVkQXQiOiIyMDI2LTAyLTIzVDEwOjAwOjAwWiIsImlkIjoiNDEyIn0=&limit=20{
"items": [/* 20 posts */],
"pageInfo": {
"nextCursor": "eyJjcmVhdGVkQXQiOiIyMDI2LTAyLTIzVDA5OjU5OjM4WiIsImlkIjoiMzkzIn0=",
"hasMore": true
}
}Advantages
- Stable ordering for changing datasets
- Great for infinite scroll/timelines
- More efficient for large datasets
Disadvantages
- Hard to jump directly to page N
- Requires deterministic sort keys
- Total count is expensive / often omitted (can be stale on real-time feeds)
Backend Query Pattern
Offset SQL
SELECT id, created_at, title
FROM posts
ORDER BY created_at DESC, id DESC
LIMIT 20 OFFSET 400;Cursor SQL (keyset pagination)
SELECT id, created_at, title
FROM posts
WHERE (created_at, id) < ($1, $2)
ORDER BY created_at DESC, id DESC
LIMIT 20;Interview Answer Template
“For a live feed, I’d use cursor-based pagination with (createdAt, id) as the cursor key to avoid duplicates/skips while new items arrive. For an admin table where users jump to page 27, I’d use offset pagination.”
Mention one tradeoff and one mitigation:
- Tradeoff: cursor can’t jump to arbitrary pages.
- Mitigation: combine cursor for feed view with search/filter shortcuts and date-based anchors.