> Not particularly. It's using the wrong tool for the job. A distributed database is helpful in many ways, but you don't need an attached proof-of-work system.

Blockchain doesn't imply PoW. You could consider each block minted with e.g. a M of N signature scheme, in the case of a stock-trading system you don't need open anonymous/participation and it's quite fine to rely on trusted parties.

I suppose, but at that point you're really blurring the line between 'blockchain' and 'authenticated database logs', and it starts to become a mere buzzword.

At this point "blockchain" pretty much refers to a hash chain, transactions signed by private keys, and some kind of distributed consensus, which could be proof of work, proof of stake, or traditional byzantine consensus if you know who all the node operators are.

Yeah, every invoicing software in my country hash chains the documents for validation purposes (it's a requirement for SAF-T[1]), yet we don't call it a "blockchain".

[1] https://en.wikipedia.org/wiki/SAF-T

Because there are no blocks, no transaction ordering and no distributed consensus?

A block is just a structure with a set of transactions, a date and the hash of the previous block. SAF-T has all that, except the "blocks" have a single transaction. Transaction ordering is provided by the chain of hashes - each record/block links to the previous, just like in the Blockchain.

There is no distributed consensus, but that's the point - there doesn't seem to be here either.

'Blockchain' pretty explicitly specifies the data structure, the method of securing a block is an implementation detail. For example Proof of Stake is basically a variation on a M of N signature scheme.

Without an incentive to "mine" blocks (cryptographically solve).. Anyone can write blocks to the network. How would the network ensure a trusted actor is writing blocks?

The way I understood the proof of work system is that it's there to determine which block is accepted as truth. So during a conflict, the first to solve the proof of work puzzle has their block accepted.

For distributed databases, when there are multiple conflicting transactions that touch the same data, I could see the proof of work as a method to determine which transactions win, especially in a global, multi-master model. When the proof of work puzzle is solved during conflicts, the transaction is accepted as truth and moves to a COMMITTED state. It seems kind of wasteful if you are paying for resources to solve challenges, but maybe there's a better way to decide who wins for trusted vs untrusted environments.

As an aside, Spanner I think acquires locks globally before writing. Maybe there's an interesting global-lock free model that just works using block chain, even if it's just for trusted parties (I.e. Google-internal).

You can have multiple winners at the same time. Proof of work doesn't solve the problem of conflicts. Everyone still has to pick which fork to follow, and you can't really consider something committed until it's buried under multiple blocks that you're confident the majority agree on.

Oh, you're right, I forgot about proof of work. I guess you can go in and remove proof of work to make a simpler blockchain. But then you're losing some of the plug-n-play aspects.