API & Systems Engineering

Custom WordPress API & Enterprise Third-Party Integrations

Connect your WordPress website to any CRM, ERP, payment gateway, custom software, or cloud API. We engineer secure, high-throughput REST and GraphQL endpoints, webhook listeners, and two-way data sync pipelines.

Core Stack: HTML5 / Modern CSS TypeScript React / Vue Tailwind / Vanilla CSS GSAP Motion Webpack / Vite
chadsia.com / services / api-and-third-party-integrations
Verified Build
Custom WordPress API & Enterprise Third-Party Integrations
99 PageSpeed Sub-Second LCP
Senior Engineering 17+ Veteran Craft
Integration Capabilities

Seamless Data Flow Across Your Entire Software Stack

We eliminate manual data entry and broken third-party plugins by engineering custom, high-reliability API pipelines tailored to your architecture.

Custom REST & GraphQL Endpoints

Develop custom, authenticated WordPress REST API endpoints tailored for mobile apps, external web portals, and microservices.

  • JWT & OAuth2 tokenized authentication
  • Optimized database query serialization
  • Custom rate limiting & IP whitelisting

Two-Way CRM & ERP Synchronization

Automate real-time customer data, order status, and lead pipeline sync between WordPress and HubSpot, Salesforce, or Zoho.

  • Bidirectional field mapping
  • Conflict resolution algorithms
  • Real-time asynchronous queue processing

Payment Gateways & Fintech APIs

Custom integration with Stripe, PayPal, Square, Authorize.net, or regional fintech providers for recurring billing and custom checkout.

  • PCI-compliant tokenized transactions
  • Custom webhooks for dispute & refund events
  • Automated invoice generation & reconciliation

Event-Driven Webhook Pipelines

Build resilient webhook listeners and dispatchers to trigger automated actions in Slack, Zapier, Make, n8n, or internal systems.

  • HMAC signature verification
  • Dead-letter queues for failed events
  • Complete event audit logging

Webhook Handlers & Async Background Queues

Resilient event-driven webhook listeners with retry queues, idempotency keys, and error logging to ensure zero data loss during traffic spikes.

  • Idempotent Webhook Processing
  • Automated Exponential Backoff Retries
  • Background Worker Queueing (Redis/Cron)
  • Detailed Ingestion Logging & Alerts

Enterprise Authentication & OAuth 2.0 Security

Secure API gateway architectures with token encryption, HMAC signature verification, rate limiting, and RBAC access controls.

  • OAuth 2.0 & JWT Secure Handshakes
  • HMAC Payload Signature Verification
  • API Rate Limiting & Abuse Prevention
  • Encrypted Credential Vaulting
Why Choose Chad Sia

Resilient Engineering vs Fragile No-Code Connectors

HMAC Encrypted

Enterprise-Grade Security

Encrypted API payloads, HMAC secret validation, and strict sanitization protect your internal databases from external vulnerabilities.

Non-Blocking

Asynchronous Background Processing

API calls are queued using WordPress Action Scheduler or Redis queues, ensuring your front-end page speed is never slowed down.

Zero Data Loss

Automated Retry & Error Logging

If an external service is temporarily down, our resilient retry queues automatically re-send payloads until confirmed.

OpenAPI Ready

Complete API Documentation

We provide clean Postman collections, OpenAPI/Swagger specifications, and developer documentation for your technical team.

Integration Case Studies

Mission-Critical API Integrations in Production

Defensible Legal Platform

Defensible Legal Platform

Architected a bespoke corporate web platform and solicitor directory with sub-second critical path rendering, strict WCAG 2.1 AA accessibility, and zero layout shift.

Solicitor Directory Semantic HTML5 TypeScript 99 PageSpeed
Atlas App

Atlas App

Engineered an ultra-responsive betting application and interactive client console with zero-bloat state management and real-time live odds visualizers.

Betting App Interactive UI Modern JS Custom API
Casa Halo

Casa Halo

Designed and built an ultra-premium booking portal for luxury vacation rental villas with fluid typography, immersive visual storytelling, and direct reservation inquiries.

Vacation Rental Villa Custom WordPress Fluid Typography Sub-Second
BluSonil

BluSonil

Developed a health and wellness spa platform with sub-second treatment showcase pages, interactive service selection, and streamlined direct booking.

Health and Wellness Spa Sub-second LCP Conversion UX
GypsyJazz

GypsyJazz

Custom WordPress media and learning platform with gated video masterclasses, music courses, lessons, and fast streaming audio player integration.

Music Courses and Lessons Custom WordPress Fast Media A11y AA
Broco Energy

Broco Energy

Built a high-traffic industrial fuel, commercial HVAC, and energy marketing website with dynamic delivery dispatch forms and commercial quote calculators.

Fuel & HVAC Marketing Custom PHP CRM Integration Sub-Second TTFB
API Roadmap

Our 4-Step API Engineering Methodology

01

API Contract & Data Schema Specification

We analyze endpoint documentation, define JSON payload contracts, authentication protocols, and error response standards.

  • API Architecture Blueprint
  • JSON Payload Contract Spec
02

Endpoint Development & Sandbox Testing

We build custom REST/GraphQL endpoints, implement tokenized authentication, and test in isolated staging sandboxes.

  • Functional API Endpoints
  • Postman Test Suite
03

Queue & Asynchronous Handler Implementation

We configure Action Scheduler background workers, automated retry mechanisms, and error alert telemetry.

  • Asynchronous Queue Engine
  • Automated Error Retry System
04

Security Audit, Load Testing & Handover

Penetration testing against API endpoints, high-concurrency throughput testing, and full technical documentation handover.

  • Security & Concurrency Report
  • OpenAPI Documentation Handover
Senior Backend & API Engineer

Direct Collaboration with a Senior API Architect

Chad Sia specializes in building scalable backend architectures and API integrations. You work directly with an experienced engineer who understands database transactions, data security, and high-concurrency performance.

17+
Direct Craft
0%
Middle-Men
100%
Custom Code

"We treat every line of code as an investment in your business speed, security, and conversion metrics."

CS

Chad Sia

Founder & Principal Engineer · Since 2009
Verified Client Proof

Rated 5.0 on Google Reviews

5.0
5 Google Reviews
Review on Google
Google Review

“I had a great experience working with Charles Sia Media. Charles was professional, responsive, and really easy to work with from start to finish. He understood exactly what I was looking for and delivered a clean, well-structured website that matched the brief perfectly. What stood out most was his communication and attention to detail, he kept me updated throughout the process, made changes quickly, and genuinely cared about getting the final result right. The turnaround time was also excellent. If you’re looking for reliable, high-quality web design work, I’d highly recommend Charles Sia Media. Will definitely be working with him again.”

IS
Ismail Saleem
Verified Client · 8 months ago · 1 Google review
Google Review

“We've been working with Chad for a long time now. He handles all our web design and we love him. He's a great guy and super easy to work with - and very responsive for those times where we need urgent help in a pinch. Chad is an absolute pleasure to work with!”

GJ
GypsyJazz Secrets
Client & Partner · 9 months ago · 4 Google reviews
Google Review

“I had a great experience working with Chad Sia on web design and WordPress development. Chad built a professional, easy-to-navigate website with a strong focus on conversions. The layout, calls to action, and overall user experience were thoughtfully structured to help turn visitors into leads. Highly recommended if you need someone who understands both WordPress development and conversion-focused web design.”

TP
Tech P3Music
Verified Client · Recent · Google review
Google Review

“Amazing work and completed the project in a timely fashion! Highly recommend!”

KK
Kevin Koeppel
Verified Client · 9 months ago · 13 Google reviews · 3 photos
Google Review

“legit and hassle free”

DK
dVillain .Kalaban
Local Guide · 8 months ago · 2 Google reviews · 11 photos
Verified Review

“Charles provided fast service 2-days ahead of schedule. He communicated well with me and frequently. He took feedback and adjusted the site to my requirements. A pleasure to do business with and I highly recommend him for web-site design.”

BW
Barry W.
Verified Client · Dec 14, 2025 · Web Design Client
Common Inquiries

Frequently Asked Questions

Can you connect WordPress to custom proprietary internal software?

Yes. We can integrate WordPress with any custom software or legacy database via custom REST endpoints, GraphQL APIs, SOAP/XML feeds, or secure SQL connection bridges.

How do you prevent third-party API delays from slowing down the website?

We use asynchronous background queue workers (such as Action Scheduler and Redis). External API calls are processed off the main rendering thread, ensuring users experience instant page loads regardless of external API response times.

What happens if a third-party CRM or ERP goes down temporarily?

Our system queues failed webhook events in a persistent database table and automatically retries with exponential backoff once the external service recovers, ensuring zero lost leads or orders.

Do you provide API authentication via OAuth2 or JWT?

Yes. We implement secure tokenized authentication using JSON Web Tokens (JWT), OAuth2, or HMAC request signing with encrypted secret keys.
Connect Your Software Stack

Ready to Engineer High-Reliability API Integrations?

Book an API strategy call to review your data flow requirements and receive a comprehensive technical architecture blueprint.

Book Your API Strategy Call