Shipping Crypto-to-Crypto on Binance

CoinSwitch only supported fiat-to-crypto trades. Adding crypto-to-crypto meant integrating directly with Binance's trading engine. I owned this end-to-end — from API design to cross-team coordination — resulting in a 2.77% increase in cryptocurrency market share.

System Architecture

  ┌──────────┐    ┌──────────────┐    ┌───────────────┐
  │  Mobile  │───▶│  CoinSwitch  │───▶│   Binance     │
  │   App    │    │   Gateway    │    │   Exchange    │
  └──────────┘    └──────┬───────┘    └───────┬───────┘
                         │                     │
                  ┌──────▼───────┐      ┌──────▼───────┐
                  │    Order     │◀────▶│   Binance    │
                  │  Management  │      │  WebSocket   │
                  │   Service    │      │   (Price)    │
                  └──────┬───────┘      └──────────────┘
                         │
              ┌──────────┼──────────┐
              │          │          │
        ┌─────▼────┐ ┌──▼───┐ ┌───▼────┐
        │ Validate │ │Match │ │Settle  │
        │  Order   │ │Order │ │ Trade  │
        └──────────┘ └──────┘ └────────┘

Key Challenges

Price Volatility

Crypto prices can move 5% in seconds. The system locks the price at order creation and has a configurable TTL (time-to-live). If the order isn't executed within the window, it's automatically cancelled and the user gets a fresh quote.

Binance Rate Limits

Binance enforces strict rate limits per IP and per account. The system uses a priority queue for order execution — market orders get priority over limit orders, and the rate limiter (the same library I built) ensures we never exceed Binance's thresholds.

Cross-team Coordination

This touched the mobile team, risk team, compliance, and finance. I set up weekly syncs, wrote a detailed RFC, and maintained a shared Notion doc with the complete state machine for crypto-to-crypto order lifecycle.

Order State Machine

  CREATED ──▶ VALIDATING ──▶ MATCHING ──▶ SETTLING ──▶ COMPLETED
     │             │              │            │
     └─── CANCELLED ◀─────── FAILED ◀─────────┘

Impact

2.77% increase in crypto market share. The feature shipped in 6 weeks and has since processed millions of crypto-to-crypto transactions on the platform.