Neljohn Cerera
Client projectNestJSNext.jsPostgreSQLLegacy migration

Members Information System

  • Client project
  • Full-stack
  • On-premise
  • Solo built

The cooperative's core system of record — member and account data that almost every other workflow depends on — rebuilt from a years-old, heavily patched desktop application into a modern three-tier web platform. Diagnosed the real performance problem, kept the business rules that worked, and migrated the data and the users across, solo.

Solo builtDesktop → web migrationOn-premise · Docker
Under NDA

Client project — implementation details confidential

Internal workflows, data models, and system-specific flows are omitted out of respect for client confidentiality. Happy to walk through the architecture and approach on a call.

What I built

The capabilities behind the platform

  • Three-tier architecture

    Next.js client, NestJS API enforcing every business rule, and a relational database as the single source of truth — domain logic in dedicated policies and use cases, not controllers.

  • Member & account system of record

    Central member and account master data, status and history tracking, and the lookups the rest of the cooperative's systems build on.

  • Performance diagnosis, not rewrite-for-its-own-sake

    Traced the legacy slowness to missing database indexes rather than the queries themselves — search went from seconds to instant while the proven logic was preserved.

  • Legacy data migration

    Import pipelines around the old system's exports — field mapping, record validation, and mismatch reconciliation before anything touched the new database.

  • Safe-by-default writes

    Transactional integrity on every write that matters, audit logging on anything sensitive, and soft-deletes throughout so a mistake is always recoverable.

  • Offline-first deployment

    Dockerized for on-premise, low-connectivity environments — Nginx reverse proxy, health checks, and its own private-cloud server.

Skills demonstrated

What this build exercised end to end

  • Legacy system analysis & domain reverse-engineering
  • Full-stack development (NestJS + Next.js + TypeScript)
  • Relational DB design, indexing & query performance
  • Data migration & reconciliation pipelines
  • Clean / layered architecture & domain-driven design
  • Transactional integrity, audit logging & soft-delete
  • Containerized, offline-capable deployment (Docker, Nginx)

Tech stack

Each tool and the job it does here

Backend API

NestJS

Web client

Next.js · React

Full stack

TypeScript

Database

PostgreSQL · TypeORM

Deployment

Docker · Nginx

CI/CD & deployment

Release-driven · Registry-based · On-premise

  1. 01

    Tag a GitHub Release

    Triggers the pipeline automatically

  2. 02

    GitHub Actions

    Build web + server Docker images via multi-stage builds → slim, runtime-only images

  3. 03

    Push to Docker Hub

    Versioned, immutable image tags → reproducible deploys and easy rollback

  4. 04

    On-prem server

    docker compose pull → up -d, behind Nginx

Let's work together

Have a product to build?

I'm available for full-time roles and select contract work. Tell me what you're building and I'll get back within a day.

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