Sequel keeps user data in cloud storage services (may change with operational requirements).
For publicly accessible resources, like NFT metadata and digital artifacts, Sequel uses IPFS.
Distributed Ledger that powers ChainLocker utilises Hyperledger Fabric, an open source, permissioned blockchain framework, started in 2015 by The Linux Foundation. As Sequel platform matures, we may decide to switch to a public blockchain, such as Flow, to fully open the underlying ledger data and enable a new generation of self-hosted Sequel clients. Thankfully, ChainLocker framework supports such transition seamlessly.