Problem Statement: Multi-Venue Swap Aggregator
Problem Statement: Multi-Venue Swap Aggregator — token swap aggregator interview depth
Problem Statement: Multi-Venue Swap Aggregator
1inch/Paraswap/Matcha-class swap aggregator with non-custodial swaps, pooled liquidity, and router-based routing. Design a Uniswap-class token swap aggregator where traders swap ERC-20 tokens without custodians. Liquidity lives in on-chain pools; prices emerge from the constant-product invariant \(x \cdot y = k\) (or stable-swap curves for pegged assets). Interviewers expect you to separate settlement truth on-chain from indexer/API projections that may lag one block.
Mechanism
- Non-custodial swaps with wallet-signed transactions
- AMM pools instead of centralized order books for MVP
- Composable with routers, aggregators, and LP tokens
- Ethereum mainnet + L2 deployment assumptions
Settlement invariants
Pool reserves update atomically; k never decreases except fees accruing to LPs. Off-chain quotes must re-simulate against the block tag users will sign.
Failure modes
- sandwich on large trades with tight slippage
- fee-on-transfer tokens breaking balance checks
- indexer lag showing stale price impact
- reorg double-applying Swap events
Interview checkpoint (sec-01)
State best executable route, simulation block tag, and minReturn slippage guard when discussing problem statement: multi-venue swap aggregator—not a single-pool AMM lecture.n-custodial swaps with wallet-signed transactions, AMM pools instead of centralized order books for MVP, and Composable with routers, aggregators, and LP tokens** when a 1inch/Paraswap interviewer probes understanding depth—not generic Web3 hand-waving.
Staff+ talking point
Staff+ move: quantify reserves, fee bps, and revert rate before naming cloud SKUs—keeps the answer anchored in on-chain truth.
1 public final class PairReserves { public final long reserve0; public final long reserve1; }
1 TVL_USD = 8_000_000_000 # illustrative Aggregator TVL
1 export function getAmountOut( 2 reserveIn: bigint, 3 reserveOut: bigint, 4 amountIn: bigint, 5 feeBps = 30, 6 ): bigint { 7 const inWithFee = (amountIn * BigInt(10_000 - feeBps)) / 10_000n; 8 return (inWithFee * reserveOut) / (reserveIn * 10_000n + inWithFee); 9 }
Aggregator focus (sec-01)
Design a 1inch / Paraswap / Matcha-class token swap aggregator that scans dozens of on-chain liquidity venues (Uniswap v2/v3, Curve, Balancer, Sushi, etc.) and returns the best executable route for a wallet swap. Unlike building a single AMM, you orchestrate off-chain pathfinding plus on-chain execution through one aggregation router contract. Interviewers probe whether you treat quotes as simulations and chain state as truth.
Interview checkpoint (sec-01)
State best executable route, simulation block tag, and minReturn slippage guard when discussing problem statement: multi-venue swap aggregator—not a single-pool AMM lecture.
Why interviewers care
Token Swap Aggregator interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.
Interview checkpoint
Name one failure story for Problem Statement: Multi-Venue Swap Aggregator that proves you understand real outages, not happy-path diagrams.
Key Highlights
- •Pathfinder scans multi-venue liquidity graph
- •eth_call simulation before wallet signs
- •AggregationRouter executes split routes on-chain
- •Indexer confirms realizedOut vs quotedOut
Section Rescue Kit
Buzzwords to use:
Safe statements:
- "For Problem Statement: Multi-Venue Swap Aggregator, I'll state reserve invariants before naming cloud SKUs."
- "I'll walk quote → simulate → sign calldata → indexer receipt when stuck."