Yeah, that is definitely a limitation with QAT. It isn't a great fit for larger data, as it can quickly lose compression ratio due to its smaller window. However, there is a lot of compression done on data that is <64KB. E.g. compression in RocksDB.

We also have some half baked ideas to combine a fast SW match finder that only looks for matches >64KB away, and supplements the matches that QAT finds.