What is the maximum length of a cache value?

In Catalyst Cache, the maximum length of a cache value is 16,000 characters. A cache item is a key-value pair stored in a cache segment, with a keyname, a value and an expiration time in hours. The Insert and Update Key-Value APIs also list 16,000 characters as the maximum size of cache_value. You can see the total size of each segment under Cache in DevOps Metrics.

Refer to the Cache Key Concepts help page and the Insert Key-Value in Cache Segment API page for details.