Next in the studio, we caught James O'Beirne, who until recently was a co-worker of ours at Chaincode. We talked to James about his experience at the Chaincode residency, his most recent project Assume UTXO (GitHub issue, proposal, talk) and how he champions and effects change in Bitcoin Core. Discussed in this episode: - 2018 residency (2:42)  - Choosing what to work on (5:40) - Fork detection framework (6:55) - Initial block download (IBD) (8:10)  - What a node does during IBD 1110 - DNS seeds (11:30) - UTXO set (12:30)  - Parallelized signature validation (14:20)  - Assume valid (14:40)  - Different than checkpoints (17:30)  - Updating assume valid value in the code (0.19, 0.18) (19:00) - Assume UTXO (21:20)  - Platform and memory considerations (27:15) - Criticisms (27:55) - Championing a big change in Bitcoin Core (32:20) If you like this, find more shows at podcast.chaincode.com. Thank you to Matthew Zipkin for sound engineering.