Integration Architect & Engineering Leader Nairobi, Kenya (UTC+3) · walterokumu.github.io · LinkedIn · okumu.oriaro@gmail.com

I design and run the systems that sit between other systems — payment rails, CRMs, ERPs, analytics platforms and directory data — for a multi-country business operating across seven markets.

Currently Head of Product Development at Yellow Pages Group, reporting to the CEO and COO, with technical ownership of the group's product platform across Kenya, Cape Verde, Mozambique, São Tomé, Angola, Tanzania and East Timor. I lead a small engineering team, set the architecture and quality standards, and still write and review the code.

Fourteen years in software, the last four spent almost entirely on systems integration: making things that were never designed to talk to each other work together reliably, across borders, in low-bandwidth markets, on infrastructure we run ourselves.

Multi-system integration platform — A spec-first integration hub fronting more than twelve external systems: a website platform, a listings platform, three Google data APIs, transactional email, object storage, a CRM, an ERP, a reporting service and a legacy Oracle registry. Fastify and Node on the backend, Next.js on the front, PostgreSQL and Redis behind it, with a 16,000-line OpenAPI contract that generates the shared types. Governance is part of the product: scoped API keys, key rotation, feature flags, integration health monitoring and an encrypted-column layer.

Payment gateway abstraction — A payments backend where every provider is an adapter behind one interface: capability negotiation, checkout construction, callback handling and refunds. Adding a market is one new file and one line in the registry. Running in production across two countries and three gateways, including a direct M-Pesa Daraja integration and card acquiring with EMV 3DS 2.2.0.

Governed data access for AI tooling — A read-only platform gateway exposing four datastores (PostgreSQL, MySQL, Oracle, Redis) to AI agents and internal services, with the read-only guarantee enforced at the SQL-parse layer rather than by convention, and designed to run VPC-internal with no outbound egress.

Client integration consulting — Lead intake middleware for a Portugal-based client, delivered with a written decision record, an explicit scope boundary, thirteen architecture decision records, an operational runbook and a downstream CRM push that ships built but configuration-gated, because the client's CRM is mid go-live.

Most of this work lives in private repositories. I write about the architecture publicly instead — see integration-architecture-notes.

Specification before implementation. Architecture decisions written down and dated, including the ones that turned out wrong. Conventional Commits enforced in CI, protected branches, tag-triggered deploys, automated versioning. Documentation treated as part of the change, not a follow-up. Mobile-first and WCAG 2.1 AA on anything with a UI.

I have an ISO 9001 habit for process, ISO 31000 for risk and ISO 27001 for security hygiene — applied at the scale a small team can actually sustain, not as paperwork.

Backend Node.js · Fastify · Express · PostgreSQL · Redis · Oracle · MySQL · OpenAPI Frontend Next.js · React · TypeScript / JavaScript · Tailwind CSS Infrastructure Docker · GitHub Actions · self-hosted CI runners · PM2 · Apache2 · Linux VPS · MinIO · AWS (EC2, S3, RDS) Integration REST and webhook design · adapter and registry patterns · queue-backed jobs (BullMQ) · payment rails (M-Pesa Daraja, SISP, card/3DS) · CRM and ERP connectors AI Model Context Protocol servers · agent tool registries and memory · pgvector / RAG · LLM routing

Mentoring full-stack developers at Microverse since 2022 — weekly code review covering architecture decisions and real-world engineering standards. Three mentees have gone on to their first developer roles.

Building ContentFloa, an AI content marketing platform for Small & Medium Businesses.

Working toward AWS Solutions Architect – Associate.