Implementing Pull‑Down Pagination for Instant Messaging History

Hello, I am programmer Yu Pi. My junior asked for a practice project idea, and we decided to build a simple instant‑messaging (IM) system to explore core features like sending and receiving messages.

When asked how to let users view their historical messages, the junior suggested loading all messages at once, but we explained that with potentially hundreds or thousands of messages, full loading would be slow, so pagination is required.

How to Implement Pull‑Down Pagination?

Business Scenario

In IM applications (e.g., chat rooms), users typically load recent messages first and then pull down to fetch older messages. Unlike standard pagination that shows a single page of data, pull‑down pagination loads data incrementally, appending new batches to the existing list to create an infinite‑scroll experience.

For example, with 10 messages and a page size of 5, the client initially loads the latest 5 messages. After pulling down, it loads messages 6‑10.

Problems with Traditional Pagination

Traditional pagination relies on page numbers or offsets. If new messages arrive between page requests, the offset‑based query can return duplicate or missing records because the underlying data set has shifted.

For instance, after loading the first page (messages 1‑5), five new messages arrive. When the client requests the second page using LIMIT 5,5 , it may retrieve the newly arrived messages instead of the intended older ones, causing duplication.

Therefore, offset pagination is not suitable for real‑time chat histories.

Recommended Solution – Cursor Pagination

Cursor pagination solves this issue by using a stable cursor (e.g., the primary‑key ID or timestamp) instead of an offset. After each query, the client records the last message's ID and sends it as the cursor for the next request.

This approach ensures that newly inserted messages do not affect the ordering of previously fetched pages.

When loading the next page, the backend runs a query such as:

SELECT * FROM messages
WHERE id < :cursorId
ORDER BY id DESC
LIMIT 5;

Only messages with IDs smaller than the cursor are returned, guaranteeing consistent pagination even as new messages arrive.

Extended Knowledge

Cursor pagination is a classic technique widely used for incremental data loading in high‑volume scenarios, including social media feeds, recommendation systems, and data migration tasks, beyond just IM history retrieval.