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MetaMask provides an extension to add a wallet feature to your browser so that you can interact with dapps. This was the first project to provide this feature back in the day, but it's now quite outdated; A much better alternative would be Frame. A wallet needs an RPC node to talk to, and a new user doesn't want to have to worry about this, so MetaMask uses Infura as their default. But you can go into settings and change it, either to your own node or to a node hosted by someone else.
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InfluxDB
Purpose built for real-time analytics at any scale. InfluxDB Platform is powered by columnar analytics, optimized for cost-efficient storage, and built with open data standards.
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Infura provides what's called an RPC endpoint. RPC is the way you expose a node to people who want to talk to it from a web browser etc. You can run your own node, using a normal computer, but it needs a big SSD drive (around 2TB) which costs a couple of hundred dollars. If you want to use a node hosted by somebody else, there are lots of other companies providing them. A good one is Alchemy. You can see a long list of publicly available RPC nodes for Ethereum (and also similar lists for other chains) at https://chainlist.org/
