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HARDIL SINGH
Lead Full-Stack Engineer / TypeScript · Node.js · PostgreSQL

Hardil Singh

I build software that can't lose data: crypto payments and custody, a trading ledger, Posthaste (a transactional email service with its own mail servers) and an AI agent that runs inside an HR SaaS. I design the architecture, write most of the code and take it to production.

singh.hardil.dev@gmail.com LinkedIn GitHub Posthaste BitDecentro
Experience8+ years
BasedÎle-de-France, France
Looking forSenior / lead role in France
StackTS · Node · React · PostgreSQL

Selected Work

07 products

Lead engineer on each, from the data model to deployment. Bitopayments was co-built with a partner; Palladium was built for a client; Doma was client work at Antier.

01
Posthaste
Liveposthastemail.dev ↗
Email infrastructure · own product
Transactional email service on its own inbound and outbound mail servers: 115-endpoint API, SDKs in five languages, load-tested with nearly a million messages.
02
Bitopayments
Livebitopayments.com ↗
Payments infrastructure
Crypto payment gateway for EVM chains and Tron: checkout, dashboards, backend and contracts.
03
MPC Custodial Wallet
Livempc.bitopayments.com ↗
Key management · custody
B2B threshold-MPC custody — a swappable signing core and configurable per-share key storage.
04
Palladium
LiveCase study →
Trading platform · client project
Commodity and index trading on an append-only, hash-chained ledger: margin, liquidation and P&L.
05
Doma
Livedoma.io ↗
Real-world assets (RWA)
On-chain retail of physical gold & silver — RWA with on-chain settlement.
06
DecentroHR
Livedecentrohr.com ↗
AI-first SaaS · HRMS/ERP
Multi-tenant HR SaaS with Sana, an AI agent in production that runs 350+ business actions with human approval for anything sensitive.
07
Token Deployer
PrivateCase study →
Web3 tooling
Multi-chain ERC-20 / TRC-20 deployer (CLI) with a deployer-only timed-burn expiry model.

How I Build

With AI agents, not by them

I use AI coding agents (Claude Code) every day to move faster on implementation and code review. The architecture, the invariants, the technical decisions and what goes to production stay with me, and every change still passes tests and review.

01 / Plan

Spec & architect

Frame the problem, data model and hard invariants with Claude before a line is written.

Claude · Opus
02 / Build

Agentic build

Implement with Claude Code — tiered delegation (plan → execute → synthesize) across parallel work.

Claude Code
03 / Verify

Tests alongside

Unit, integration and e2e written with the code; typecheck + build gates; hooks catch footguns.

vitest · Playwright
04 / Review

Adversarial review

Automated passes — correctness, money-path audit, security — then human judgement.

code · money · security
05 / Ship

CI/CD

GitHub Actions → GHCR → docker-compose / Terraform + ECR; Nginx + Cloudflare.

GitHub Actions
↻ Tight feedback loop — failures route back to plan. Result: faster delivery, with tests and review at every gate.

Reference architecture

How a money-critical service is wired — the pattern behind custody, payments, trading and email.

Clients
React / Next.js · React Native · browser extension — httpOnly sessions, CSRF, TOTP 2FA
API — NestJS
Typed REST / GraphQL + WebSockets; auth guard; request path kept fast and decoupled
Audited choke-point
Every money / state mutation routes through one audited function; the ledger is truth, caches mirror it
Durable queue
Redis / BullMQ — backpressured, batched writer keeps the hot path off the DB; nothing drops under load
Ledger + database
Append-only, hash-chained ledger (tamper-evident) + PostgreSQL; monotonic sequence, gaps detectable
Custody — MPC
Frozen signing seam; threshold-MPC (Go / Taurus); keys never whole; per-share storage across clouds
Secrets & deploy
Cross-cloud secrets (AWS + GCP) · GHCR → compose / Terraform + ECR · Nginx + Cloudflare TLS

Writing

dev.to ↗ / 8 posts
Production
engineering
DevOps
& security
AI-augmented
workflow
Environment
& tooling

Also Built

Earlier work
TOMI WalletMobile crypto wallet with encrypted real-time chat. 50,000+ downloads on Google Play (Antier).
Streak WalletHybrid CeFi/DeFi wallet with a cross-protocol yield-rewards system.
dApps & extensionsDEX, DAO and staking platforms, plus a Web3 wallet browser extension.