A ScyllaDB engineering post about a new io_uring backend for Seastar that breaks the usual shared nothing rule, where every core does its own I/O and compute. The asymmetric backend instead sets aside a few cores as dedicated networking workers while the rest run only application logic, and routes I/O syscalls to those workers through io_uring queues. To make it work the team had to remove a speculative fast path that let a shard skip io_uring and issue a plain syscall on its own core, since that shortcut defeats the point of offloading. The numbers are honest about the tradeoff: raw I/O throughput trails the older linux aio backend, but compute shards get back the CPU time they used to spend on sockets and disk calls.