In our solution we present a whitelisted (0 gas tx) example, where all xDai-centric transactions are free for users and for Reddit administrators. This includes token distributions, claiming, subscriptions, burns and transfers. Bridge costs are discussed below.
Under ordinary circumstances, transactions on xDai are stable at 1GWei, and there are 1,000,000,000 GWei per xDai. To calculate price per transaction, we multiply the gas cost by 1,000,000,000. This is easily converted to USD, as 1 xDai = 1 USD. Since xDai is a stable chain, transactions costs do not vary based on external currency fluctuations.
With 300,000 tx the user's transaction costs are trivial (amounting to ~$1.60/validator). However, when scaling to 100M+ users, costs can add up. Full scale volume discounts will apply with user base size increases.
~ Gas per Transaction
~ USD cost/tx non-whitelisted
Avg for Load Test
# Performing Operation
~ Cost for 100K Users (300K tx)
100,000 / 100%
25,000 / 25%
75,000 / 75%
100,000 / 100%
The qDai chain is natively implemented with 0 tx fees and 0 block rewards, resulting in substantial savings for a large user base over time.
There are some user-based costs associated with bridging tokens to and from the Ethereum Mainnet. Bridging will not be necessary to access everyday token functionality (transfers, subscriptions, etc), but only to access additional functionality or liquidity on Ethereum (or other connected chains).
Bridge transactions from xDai to Ethereum can be subsidized by bridge validators, however Eth would be required to pay gas fees to bridge tokens back to xDai. A fee manager can also be configured to collect a percentage of the total amount bridged by users (ie in MOON tokens) in either direction. The fee manager is configurable and can be adjusted as needed.
Depending on the chosen solution, Reddit community points can be pre-minted on Ethereum to save gas costs when bridging (rather than minting on demand). The minting strategy should account for anticipated bridge use.