The Glitter Bridge consists of two completely separated deployments in Frontend and Backend with no direct communication or even having a notion of each other.
The Frontend is responsible for sending requests to each side of bridge related blockchain as well as waiting for the status finalization on the other side by listening for smart-contract program updates or checking the associated wallet's local state (depending on the chain mechanism and functionalities).
On the backend nodes, emitter (PubSub design pattern) agents are listening to smart contracts on each chain waiting for new approvals to emit them to the other side's subscriber agent, and then the other side's node would use an oracle transaction to update the smart contract states and give back an ACK message to the publisher on originating side.
On frontend, bridge process fulfillment will be followed through listening to smart contract transactions finalization with associated specific signatures of the exact bridging process started by the very same frontend instance.
For token mechanisms in place, it also varies depending on the chains. For Algorand LOCK/RELEASE is used while on Solana MINT/BURN is being utilized.