Write a cache cleaner for a file system

efs_cache_cleaner/README.md

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+# efs_cache_cleaner
+
+This service allows us to purge our EFS cache based on the age and size of items.
+
+Some of our ECS applications use local storage as a cache (for example, Loris).
+Because ECS instances have very little disk space, we use an EFS mount rather than the host disk.
+However, EFS storage has a price – although it can grow to any size, it would be expensive to let it do so!
+This service deletes files from our EFS cache to keep our costs sustainable.
+
+Our caches are bounded by two configurable:
+
+*   **maximum age** -- if an item is in the cache but hasn't been accessed for more than 30 days, there isn't much value in keeping it in the cache.
+    We can delete it, and re-fetch it the next time it's requested.
+
+*   **maximum size** -- EFS storage is priced based on how much you use.
+    If the cache exceeds a given size, we can delete items from the cache until it comes back under the limit.
+    Items are deleted in order of last access time -- items which haven't been accessed very recently are deleted first.
+
+Both of these parameters are configurable.
+
+Although we're using EFS, a lot of the core logic could be repurposed to run against a conventional file system.