Order of Txns
The most important thing that consensus is trying to solve, whether it's blockchain or any kind of distributed system, is to get a sequence of transactions (or events) that all nodes agree on.
There are many types of consensus used, such as PoW (Proof of Work) and PoS (Proof of Stake). All of them are slow and costly.
In the TEA Project, we use the physical value of time from GPS satellites as the source of timestamps. All events attach a TPM protected timestamp when sending to different distributed replicas. All replicas can get the same order regardless of geolocation and network latency.