Ongoing freelance work on gold and cryptocurrency trading, with a focus on wallet consistency and live market data.
My role: Freelance backend developer for trading and payment systems
Scope: Gold/tether/melted-gold orders, live pricing, chart history, wallets, crypto gateways, provider/admin operations
The problem
Trading requests and payment callbacks can overlap or repeat. Wallet balances and transaction records need to stay consistent while prices continue to change.
My contribution
I implement atomic balance updates and idempotency safeguards for wallet operations, alongside NestJS order/payment services, Socket.IO updates, Redis pub/sub, and Bull jobs. I also contribute regression tests and deployment support.
Engineering decision
Market freshness and financial correctness need different rules
Approach
Separate price/chart delivery from durable order, wallet, and payment records. A market tick can become obsolete; a transaction record must remain auditable.
Alternative and tradeoff
Treating wallet updates like transient socket events makes reconnects, duplicate callbacks, and provider timeouts difficult to reconcile. Making every tick a financial transaction adds cost without the same correctness benefit.
Reviewing the behavior
The useful review cases are duplicate provider callbacks, simultaneous balance changes, stale prices, delayed confirmations, and reconnects. Trace each case to its durable record and reconciliation path. This is a review checklist, not a claim that a published test suite covers the private product.
Measurement and scope
Client-owned implementation; scope covers the documented order, wallet, pricing, gateway, and operational workflows. No public throughput, transaction-volume, or financial-compliance certification is claimed.