Data consistency is overrated

E.g. lets say your system is storing billing records for an API. Customers won't complain about being under-charged, so a loss of data for a system like that is fine as long as reducing the durability saves more money than it costs in losts ability to charge your customers. E.g. if rolling up and syncing summaries to disk every 10 seconds were to on average lose you 0.1% of records but cut your server cost for that system by 80%, it's a simple question of whether those server costs are higher or lower than .1% of your revenue (all numbers taken out of thin air).

We make sacrifices in terms of both consistency and durability and all kinds of things all the time. The problem is that we often don't take the time to analyse what kind of inconsistency and loss is acceptable from a business point of view before designing a solution that often tries to aim for a level of consistency or durability that may not be needed.

You can afford to sacrifice all kinds of guarantees as long as you have reliable models for how sacrificing them impacts you and your customers so that you know the sacrifices represent acceptable tradeoffs. The risk you're taking is that you're sacrificing safety margins, and so it's something you should only do if you understand both the domain and your systems failure modes very well.

Imagine that you create a multiplayer MMORPG video game with a 'limited' number of virtual gold coins and you set the supply at 1 billion gold coins and you decide to track account balances using 1000 different systems managed by different companies (which constantly credit and debit each other using different mechanisms) instead of just 1 system managed by 1 company... What are the odds that you will still have only 1 billion gold coins in circulation in one year's time? Surely at least 1 of the 1000 systems will go rogue and start inflating the currency supply; it may start sending fake coins to other systems and the other systems won't be able to know that they are fake since they all operate on mutual trust instead of cryptographic proofs, they will unwittingly propagate records of those fake coins to other systems as if they were real. This is essentially how the fiat monetary system works.

The power of money creation is not supposed to be in the hands of private institutions, yet because currency is tracked across so many different systems and there is no universal consistency between them, money creation seems to be essentially guaranteed to occur; especially when you consider that the incentive is to turn a blind eye to errors which benefit large institutions.

So to say consistency is "overrated" is nonsense. It's not always 100% applicable, but this comes at a cost.