I've read Scalability on Stellar Network. My question is what's the max achievable practical value for tps using today's hardware? You can't just increase the parameters without bound and still expect a 5 second ledger time. So how much is Stellar able to accommodate using today's hardware if you make the reasonable assumption that there is one "pay" transaction per transaction envelope.
To my mind, there are a few key factors that may constrain network TPS growth.
- Physical internet connection speed. Nodes communicate with each other to reach a consensus on transactions to include in the next ledger, and SCP quorum has less than 5 seconds to dispatch all transactions, verify them, and produce a new ledger. Third-party companies conducted a few synthetic tests on private networks showing impressive TPS, but in the real world a long ping between, say, US<>Singapore or New Zealand<>Belgium may result in slow ledger closing under the high TPS conditions.
- Low-end servers used by community validators. Currently, there are more than 60 validators on the main Stellar network, and most of them use cheap cloud servers or run the virtual machines. The increasing of
max_tx_set_sizeparameter may lead to the partial quorum disruption, as some community-supported nodes won't be able to process all submitted transactions and may lose consensus. Therefore the network upgrade requires a gradual
max_tx_set_sizeincrease to give enough time to validators for hardware upgrades.
In general, I think that the main network won't (and shouldn't) reach 1M TPS. I think that 1,000 tx/s (an equivalent of 100,000 op/s) is more than enough for a next few years.
Cases that require high throughput may be implemented using private Stellar sidechains with appropriate network parameters and low (or zero for protected enterprise networks) fees. Sidechains can periodically commit the transitional accounts state to the pubnet the same way as in Lightning channels. Pity that I have not enough time and resources to implement such thing myself, it would be quite exciting and potentially game-changing service.