Offset-based pagination in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is offset-based pagination?

Offset-based pagination is a method to divide large sets of data into smaller chunks by specifying a starting point (offset) and the number of items to retrieve (limit). It helps load data page by page.

beginner

How do you specify the page and size in offset-based pagination?

You use two parameters: offset to indicate how many items to skip, and limit to specify how many items to return from that point.

intermediate

What is a common problem with offset-based pagination when data changes frequently?

If data is added or removed between requests, the same item might appear on multiple pages or be skipped, causing inconsistent results.

beginner

Example: If you want to get the 3rd page of results with 10 items per page, what should the offset and limit be?

Offset should be 20 (because 2 pages × 10 items each = 20 items to skip), and limit should be 10 to get the next 10 items.

intermediate

Why might offset-based pagination be less efficient on large datasets?

Because the database has to skip many rows before returning results, which can slow down queries as the offset number grows.

In offset-based pagination, what does the 'offset' parameter do?

A Specifies the total number of items to return

B Specifies the current page number

C Specifies how many items to skip before starting to return results

D Specifies the sorting order of results

The offset tells the system how many items to skip before returning the next set of results.

If you want to get the first 15 items, what should the offset and limit be?

A offset=15, limit=15

B offset=15, limit=0

C offset=1, limit=15

D offset=0, limit=15

To get the first 15 items, you skip 0 items (offset=0) and limit the results to 15.

What issue can happen if data changes between offset-based pagination requests?

A You might get duplicate or missing items across pages

B The server will crash

C Pagination will automatically adjust to changes

D No issues occur

Data changes can cause items to shift, leading to duplicates or missing items in pages.

Which is a disadvantage of offset-based pagination on large datasets?

A It always returns the entire dataset

B It can be slow because the database skips many rows

C It does not allow sorting

D It requires complex client-side code

Large offsets make the database scan many rows before returning results, slowing queries.

How do you calculate the offset for page number 5 with 20 items per page?

A offset = (5 - 1) × 20 = 80

B offset = 5 × 20 = 100

C offset = 20

D offset = 5

Offset is calculated by (page number - 1) times items per page.

Explain how offset-based pagination works and why it is useful in APIs.

Think about how you might read a book page by page instead of all at once.

Describe some challenges or limitations of offset-based pagination.

Consider what happens if the data changes while you are paging through it.