Methods and systems for populating a cache memory that services a media composition system. Caching priorities are based on a state of the media composition system, such as media currently within a media composition timeline, a composition playback location, media playback history, and temporal location within clips that are included in the composition. Caching may also be informed by descriptive metadata and media search results within a media composition client or a within a media asset management system accessed by the client. Additional caching priorities may be based on a project workflow phase or a client project schedule. Media may be partially written to or read from cache in order to meet media request deadlines. Caches may be local to a media composition system or remote, and may be fixed or portable.