There are plenty of good resources online. Here are some topics you probably wouldn't see in an intro algos course (which I've actually used in my career). And I highly recommend finding the motivation for each of these in application rather than just learning them abstractly.
- bloom filter
- btree
- b+ tree
- consensus algos (PAXOS, RAFT, VSR, etc)
- error correction codes (Hamming, Reed Solomon, etc)
- garbage collection (mark+sweep, generational, etc)
- generational arena allocator
- lease (i.e. distributed lock)
- log-structured merge trees
- min-cost + max-flow
- request caching and coalescing
- reservoir sampling
- spatial partition (BVH, kd-tree, etc)
- trie
- write-ahead log