Special thanks to @vbuterin for the original idea, @djrtwo, @zilm and others for review and useful inputs. TL; DR an eth2 execution model alternative to executable shards with support of single execution thread enshrined in the beacon chain. Recently published rollup-centric roadmap announces data shards as the main scaling factor of execution in eth2 allowing scalability upon a single execution shard and simplifying the overall design. Eth1 Shard design supposes communication with data shard...
