Introduction to cache policy - Edge Security Acceleration

Edge Security Acceleration (ESA) caches static resources across distributed points of presence (POPs) to reduce origin requests and latency, while supporting dynamic policy adjustments to cater to your business requirements.

Benefits

ESA increases the cache hit ratio by implementing cache policies, such as ignoring and sorting query strings. This ensures accurate identification of identical resource requests, thus minimizing redundant origin requests.
ESA allows for dynamic adjustment to cache policies, such as bypassing the cache during phased releases or debugging sessions.
By minimizing origin requests, ESA effectively reduces network latency and improves the user experience. By optimizing network performance, ESA significantly reduces the loads on the origin server and prolongs its service life.

Development mode and default cache behavior

The default cache behavior allows ESA to automatically cache static resources, such as images, Cascading Style Sheets (CSS) files, and JavaScript (JS) files, on its POPs, reducing the loads on the origin server and improving access performance. Development mode allows for a temporary bypass of cache components to facilitate debugging or phased releases.

Enable the development mode: This bypasses cache components to directly access the origin server, ideal for debugging or phased releases.
Note
Enabling the development mode may significantly increase origin traffic. Disable development mode after you complete debugging.
Default cache behavior: ESA automatically caches static resources, such as images, CSS files, and JS files, on POPs, giving priority to client requests.

Configure the cache TTL

You can configure the browser cache time-to-live (TTL) and edge cache TTL to improve access performance and conserve server resources, leading to more efficient network management and optimization.

Browser cache TTL: By default, the TTL follows the Cache-Control header that is configured on the origin server. You can configure a TTL to override the default setting, for example, setting the TTL for static resources to 30 days. We recommend that you configure a shorter TTL for frequently accessed resources and configure a longer TTL for cold data.
Edge cache TTL: You can configure an edge cache TTL for static resources based on file directories (such as /images/*) or file name extensions (such as .jpg,.css). We recommend that you set the TTL to 3600 seconds for frequently accessed resources and set the TTL to 86400 seconds for infrequently accessed resources.

Increase the cache hit ratio

You can increase the cache hit ratio by ignoring query strings or sorting query strings. Ignoring query strings treats URLs with different query parameters as the same resource for caching, while sorting query strings ensures that URLs with parameters in different orders are recognized as the same resource after sorting.

Ignore query strings: You can use the query string feature to treat cache requests with identical URLs but different ?param=value as the same resource. For example, example.com/index.html?v=1.0 and example.com/index.html?v=2.0 are considered identical.
Sort query strings: You can use the query string sorting feature to treat cache requests with parameters in different orders as the same resource. For example, /api?a=1&b=2 and /api?b=2&a=1 are considered identical.

Advanced features

ESA provides the tiered cache and cache reserve features to help you optimize resource utilization, improve user experience, reduce costs, and reduce bandwidth pressure on the origin server.

Tiered cache: ESA provides the tiered cache feature to ensure that requests are served as fast as possible from POPs closest to clients, improving the performance and efficiency of the overall content delivery system.

Cache reserve: ESA provides the cache reserve feature to converge origin requests for infrequently accessed resources into a specified cache reserve instance, preventing the resources from being overwritten by other frequently requested resources. This feature is ideal for resources that are seldom accessed but require long-term storage. Cache reserve POPs provide dedicated disk space to ensure that files are stored according to the specified duration, thus preventing unnecessary outbound traffic fees and reducing bandwidth pressure on the origin server.