Cache Configuration


PSPDFKit Server has been deprecated and replaced by PSPDFKit Document Engine. All PSPDFKit Server and PSPDFKit for Web Server-Backed licenses will work as before and be supported until 15 May 2024 (we will contact you about license migration). To start using Document Engine, refer to the migration guide. With Document Engine, you’ll have access to robust new capabilities (read the blog for more information).

PSPDFKit Server uses two different kinds of caches to improve performance and reduce the load on the asset backend.

Built-In Caches

  • When PSPDFKit Server needs to access a PDF file via the asset storage backend, the document is cached on the local file system to speed up future access. You can configure the size of the cache using the ASSET_STORAGE_CACHE_SIZE variable.

  • When a PSPDFKit for Web client requests a document, PSPDFKit Server renders the individual pages and provides them to the client. These pages are cached in memory to speed up future rendering.

Since both caches only work for a single PSPDFKit Server node and are not shared across multiple PSPDFKit Server nodes, you can use Redis to enable a shared cache.

Redis Cache

PSPDFKit Server 2018.2 introduced the possibility of using Redis as a shared cache for rendered pages. This allows multiple PSPDFKit Server nodes to share their work, since only one has to render a document and others will be able to access the cached results. Please be aware that this only works with PSPDFKit for Web.

Check out the configuration overview for more information on how to configure PSPDFKit Server to use Redis as an additional cache.

Please note that you also have to manage and configure Redis. Examples of doing this include setting the memory limit and setting an eviction policy. We recommend the allkeys-lru eviction policy for most use cases. Check out Using Redis as an LRU Cache for more information.

When moving from a trial to a production license, we also recommend deleting all cached data, as this will prevent trial overlays from showing up in production.

PSPDFKit Server is compatible with any Redis version newer than 2.2.0.

PSPDFKit Server only supports single-node Redis deployments and Redis Sentinel deployments. PSPDFKit Server cannot be configured to use multi-cluster Redis setups directly.


Refer to the documentation on the prerendering endpoint to find out how you can render and cache documents in advance to speed up the loading of your documents even more.