Backend

What are the best practices for databases in web3? Like do we want to host as much on-chain as possible and make all the calls to the chain or de want to put into DBs

Founder of Prognoze.xyz Forecasting and media.

See farcaster as a good example. Puts only the required data on-chain, everything else is implemented in either centralized dbs or through other off-chain mechanisms.

On-chain storage is slow and scarce. Use it, but only as needed

Building paywithglide.xyz. ex Robinhood, Uber, Apple

Indeed. Would you also use a decentralised indexer i.e. the Graph to query the on-chain data or opt out for your own indexer + a fast DB infra?

Depends on the goal. To get a PoC off the ground, Goldsky/Alchemy/etc provide APIs to preprocessed data. Beyond that, either bring it in house or  indexing.co. We do distributed processing, depositing data right into your DB. You own the pipes and data running through them 😀