I cannot reproduce your gains. I'm trying to improve the performance of our web-signer for batch-processing of decrypts. 

I copied your ende.ts and replaced nostr-tools with it, absolutely no effect. In fact chrome profiler shows no time spent in base64 codec, all the time is spent on crypto stuff - keygen and cipher. 

Do you have a reproducible benchmark code that shows 4k events decrypted in 2 sec? Was your measurement made in the browser or nodejs? 

Are you sure shared key caching wasn't the trick? I added that and got significant improvement, although didn't work on measuring it specifically (my focus was on nip46 flow where other stuff is also slow).