API Pagination: Making Billions of Products Scrolling Possible
By ByteByteGo
TechnologyBusinessAI
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Key Concepts:
- API Pagination
- Offset-based Pagination (Page-based, Direct Offset)
- Cursor-based Pagination
- Index Column
- Key Set Pagination
- Time-based Pagination
1. Introduction to API Pagination
- When APIs return large datasets, pagination is essential to break the data into smaller, manageable chunks.
- Instead of sending thousands of records at once, data is sent in batches (e.g., 10 or 100 records per page).
- Benefits: Manages server load, reduces network traffic, and keeps the application responsive.
2. Offset-Based Pagination
- Definition: Uses an offset to specify the starting point for retrieving data.
- Types:
- Page-based: Sets the number of items per page and calculates the starting point.
- Direct Offset: Uses
offset
andlimit
parameters directly in the query.
- Example SQL Query: A basic offset query in SQL is shown (specific query not provided in transcript).
- Problems:
- Performance: As the offset increases, query performance degrades because the database must process every row up to the offset.
- Data Consistency: When the dataset changes rapidly, offset-based pagination can miss records or show them twice due to shifting data.
3. Cursor-Based Pagination
- Definition: Uses a cursor (typically an indexed column value) to track the last seen item and retrieve the next batch of data.
- Implementation Steps:
- Choose Index Column: Select an index column (e.g., ID) as the cursor.
- Hash Cursor Value: Hash the cursor value for security.
- Client Sends Last Seen Cursor: The client sends the hashed cursor value of the last item they received.
- Filter and Fetch Next Batch: Use the cursor to filter the data and fetch the next batch of records.
- Return Result and New Cursor: Send back the result set along with a new cursor value for the last item in the current batch.
- Client Uses New Cursor: The client uses the new cursor for their next request.
- Advantages:
- Consistency: Remains consistent even when records are added or deleted between requests.
- Performance: Works well with large, fast-changing datasets.
- Use Cases: Real-time feeds or any data that changes frequently.
4. Types of Cursor-Based Pagination
- Key Set Pagination:
- Uses an index key (e.g., primary key) to efficiently retrieve the next set of results.
- Directly accesses rows without scanning all preceding ones.
- Time-Based Pagination:
- Uses timestamps as cursors to segment and retrieve records within specific time ranges.
- Practical for applications dealing with time-series data.
5. Key Takeaway and Conclusion
- For large and fast-changing datasets, cursor-based pagination is recommended due to its consistency and performance advantages.
- While more complex to implement, the effort is worthwhile for applications requiring reliable pagination.
6. Recommendation
- The video recommends a system design newsletter for topics and trends in large-scale system design.
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