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 and limit 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:
    1. Choose Index Column: Select an index column (e.g., ID) as the cursor.
    2. Hash Cursor Value: Hash the cursor value for security.
    3. Client Sends Last Seen Cursor: The client sends the hashed cursor value of the last item they received.
    4. Filter and Fetch Next Batch: Use the cursor to filter the data and fetch the next batch of records.
    5. Return Result and New Cursor: Send back the result set along with a new cursor value for the last item in the current batch.
    6. 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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