What are the best practices for pagination in web APIs?

Web applications always deal with massive amounts of data. This means web APIs will provide too much data and if the web application does not manage this matter properly, it will bring serious issues. Increasing the loading time, security issues, and network and hardware bandwidth consumption will affect the web applications seriously and adversely. With pagination, web apps provide data in different chunks requested by the user and relatively avoid errors/issues that might affect the performance or bring security issues.

Pagination is imperative for web APIs dealing with extensive data volumes, ensuring efficient performance and user experience. Without pagination, excessive data returned in a single response can lead to sluggish loading times, particularly on mobile devices or low-bandwidth connections. This can strain server resources, impacting scalability and availability, while potentially exceeding API platform quotas, resulting in errors or additional costs. By segmenting data into manageable pages, pagination enables incremental retrieval, optimizing API performance and enhancing client experience.

Pagination in APIs is necessary to manage large datasets efficiently, ensuring optimal performance by fetching data in smaller, manageable chunks, thereby reducing server load and response times.

Pagination helps to - Improve performance - Enhance user experience - Optimizing the resource usage (resource used to retrieve and transfer data) - Prepare for scale when the data size grows - Reduce the cost of re-loading in case there is an error

# Offset Pagination: Clients typically pass a page_size (offset) and a page_number (limit) to retrieve data. ## Pros: - Client can view number of pages and jump to specific pages by page number. ## Cons: - Inconsistent: Real-time data change can affect the accuracy of pagination. - Inefficient with large datasets (longer query time) # Cursor Pagination: Clients pass a cursor and a page size in each request, where the cursor points to a specific record. ## Pros: - Offers better performance with better query strategy - Avoids issues like duplicates or skipped results seen in offset pagination. ## Cons: - Not straightforward like offset pagination and can be trickier to implement. - Limited library support.

Offset-based pagination: The user can use links such as "next", "previous", and page numbers to navigate between pages that load one page of data at a time. Two properties must be set, "OFFSET" and "LIMIT". OFFSET property can be calculated if the page_number is known: (page_number-1*LIMIT). Cursor-based pagination utilises a pointer that refers to a specific database record. Users pass "CURSOR" and a "PAGE_SIZE" on each request. If the cursor is not set, the server fetches from the first record. The cursor refers to a specific unique value in the database and if the cursor is not given, the server fetches from the first record. Depending on the scenario and the way that the data is stored, the web applications can choose the best method.

Offset Pagination can return: - page: Indicates the current page number. - size: Specifies the number of items per page. - total_items: Represents the total number of items in the dataset. - total_pages: Indicates the total number of pages based on the page size and total items. - links: Provides links for navigating to previous, next, first, and last pages. Cursor Pagination can return: - cursor: An identifier pointing to the last fetched item, allowing continuation from that point. - size: Denotes the number of results per page. - has_more: Indicates whether there are more records beyond the current page. - before_cursor (optional): Helps to paginate backward - after_cursor (optional): Helps to paginate forward

The results the APIs return depend on the usability. However, the data structure must contain specific properties letting the user navigate between pages. One of the most common data structures that is used widely is: { "successful", "error_message", "data": [ "properties to include" ], "pagination": { "total_records", "current_page", "total_pages", "next_page", "prev_page" } The "properties to include" which is returned as data, need to be chosen based on the use-case. Providing all properties impacts the performance and may bring security issues. So the properties must be chosen based on the criteria and considering the criteria that the API expects to meet. pagination property offers easy access to other pages.

Facing exceptions or errors in APIs is common and if they are not handled properly, they will bring frustrations and impact the usability of the website adversely. The APIs need to handle common errors and inform the users properly through the responses they get. Invalid input parameters, like "OFFSET" and "LIMIT" or "CURSOR" and PAGE_SIZE" or other exceptions. These error handling can be done through the codes and return the result providing useful and understandable information to the users. i.e. "successful" or "error_message" properties can be set and returned to the user. The "successful" property indicates if the API call was done flawlessly and "error_message" provides meaningful information what has happened wrong.