Magento 2.3.2 Redis cache grows very large quickly

A large multi-site Magento 2.3.2 store (4 stores, 90k products, 5k categories) running with Varnish FPC and Redis cache for Magento cache. We find that within 20-30 minutes after a full cache flush, Redis cache has over 100,000 keys, using over 300 MB of memory, and continues to grow steadily in # of keys and memory use.

In looking at the keys in Redis, about half are of the format:


and the rest are mostly of the format:


Any idea why Redis would continue to grow at a fast pace (In 24 hours we’ll see Redis using 4+ GB of memory) even with Varnish FPC enabled? Once Redis is over 2 GB in size, a cache flush will often fail due to the time it takes to try and flush millions of keys. We end of having to kill Redis manually.

Trying to understand why this M2 install has such a large M2 Redis cache…