Why use Python rather than a statically-typed language? This thing looks like it will become a resource gobbling beast that runs very slowly
Summary: Python isn't the bottleneck yet, and if it becomes one, C will become the last 1%.
I've been working on production apps in Python since 2002, including ones doing large-scale compute running 1000+ machines at once. How: 99% python, 1% C. But the trick is, you only build in the C once you've worked out all the kinks and optimized the big-picture stuff elsewhere. Python is great for not only connecting things, but rapidly iterating on algorithms and building maintainable code.
The AI / ML community has discovered this too: Python is now the most popular language in that community. Despite the heavy compute. How: most of the popular libraries have efficient C (etc) implementations under the hood.
This is exactly the philosophy we've been following at BigchainDB, with success. Python to connect things, iterate quickly in improving algorithms, and ship maintainable code. We haven't got far enough to resort to building our own C libraries yet, though many 3rd party libraries we use are implemented in C.
[EDIT] Based on the comments below, I'll now mention here too: BigchainDB wraps MongoDB, which is written in C++. And, Python 3.5+ (which BDB uses) has gradual typing, which brings many benefits of static typing to Python.
I feel that gradual typing offers the best of both worlds: rapid prototyping, but also the strictness of types where you need it.
I encourage you to give BigchainDB a whirl, it's easy: https://www.bigchaindb.com/getstarted/
How one goes about getting those characteristics is wide open. Most blockchain systems do have a full copy of the database at each server node, i.e. fully replicated. Also, they are "peer to peer" which means there is no distinction between clients and servers. (They do have SPV wallets though which is kinda similar.)
BigchainDB's focus has always been about scale. We're partly there but not fully: we are currently fully replicated but are targeting sharding to address that [1]. Where we do get scale already is properly distinguishing between between clients and servers. Servers are "super peers", decentralized among themselves. They do the heavy lifting, i.e storage. Apps don't need to run a server node; instead they simply are clients to the network, and of course can query >1 node.
[1] https://blog.bigchaindb.com/bigchaindb-developer-update-2d32...