Design Perpetual Futures - System Design | WinJob

Problem Statement: Perpetual Futures Exchange

Design a dYdX/GMX-class perpetual futures venue: leveraged exposure without expiry, collateralized by a vault, priced by mark for margin and liquidations, anchored to a spot index via funding. This section (sec-01, order 1) covers problem statement in the understanding phase.

Mechanism

Perpetual swap tracks index via funding payments
Position size notional = margin × leverage
Insurance fund absorbs shortfall on bad debt
Oracle index + mark TWAP for manipulation resistance

Failure modes

cascade liquidations during volatility spikes
oracle staleness triggering unfair liquidations
negative funding squeezing crowded longs
ADL when insurance fund insufficient

Interview checkpoint (sec-01)

Perpetual has no delivery date—funding replaces expiry
Mark price ≠ last trade; used for margin checks
Liquidation engine must be deterministic and auditable

Staff+ talking point

Unique angle sec-01: perpetual futures exchange (Problem Statement) — emphasize leveraged long/short with no expiry date and mark price drives pnl, funding, and liquidations without repeating AMM reserve templates.

Quantify open interest, funding bps, and liquidation penalty before naming cloud services—interviewers at dYdX, GMX, and Perpetual Protocol expect risk-first narration.

javaOne Dark Pro

1 public record PerpPosition(String account, long sizeBase, long entryPrice, int leverage) {}

pythonOne Dark Pro

1 def notional(size: float, mark: float) -> float:
2     return abs(size) * mark

typescriptOne Dark Pro

1 export type Position = { size: bigint; entryPrice: bigint; margin: bigint };

Why interviewers care

Perpetual Futures interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Perpetual Futures Exchange that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Leveraged long/short with no expiry date
•Mark price drives PnL, funding, and liquidations
•Collateral vault with cross-margin accounting
•Hybrid: on-chain settlement + off-chain matching optional

1	def notional(size: float, mark: float) -> float:
2	return abs(size) * mark