Spark exists because Sky wanted a distribution channel for DAI and USDS credit. It forked Aave's code, connected directly to Sky's balance sheet through the Direct Deposit Module, and can therefore supply stablecoin liquidity at rates set by Sky governance rather than by pool utilisation.
Why the rates are lower
In a normal lending market, the borrow rate rises as utilisation climbs. Spark can draw fresh DAI or USDS directly from Sky, so utilisation-driven rate spikes are dampened and the borrow rate tracks Sky's policy target. For a borrower, that means predictable, usually market-leading rates on stablecoins.
The dependency
Your borrowing cost is a governance decision at a protocol you may have no relationship with. If Sky raises its rate or reduces the credit line, Spark's rates move with it and users have no separate say. This is a real structural difference from Aave, where rates emerge from supply and demand within the market itself.
Security
The codebase is Aave's, extensively audited and battle-tested, with Spark's own modifications audited separately. No incidents since launch. Collateral standards follow Sky governance, which has been conservative on the crypto side.
Who should use it
Borrowers who want the cheapest stablecoin debt against blue-chip collateral and are comfortable with rates set by Sky governance. Depositors will generally find better rates elsewhere, since the cheap borrowing is funded by Sky rather than by lenders.