WordPress Shuttle Platform Overhaul

I run a network of airport-shuttle websites that all share a central WordPress code-base. I now need a senior full-stack developer to take the platform to the next level.

Performance goals
My first priority is speed. I want noticeably faster page-load times, a snappier server response, and clean, well-indexed database queries so high-traffic peaks no longer bog the sites down.

Booking-system customisations
The current booking engine works, but it feels dated. I want a refreshed user interface that matches each brand, a smoother booking workflow that reduces drop-offs, and tighter payment processing (covering both credit-card and wallet style checkouts). Front-end changes will be React-friendly, and the back-end must remain 100 % WordPress-native so content teams can still work without code.

API integrations
Three key integrations are pending:

• Payment gateways – Stripe is already connected; I need PayPal and Adyen added with full refund/capture logic.
• Transportation schedules – pull real-time route data from our internal REST feed and also push confirmed bookings back to it.
• User management – sync user profiles and loyalty points with our CRM’s JSON API.

Deliverables
1. A Git-based theme and plugin update that achieves <2 s average load time on GTmetrix.
2. Fully skinned booking UI with step-by-step flow, mobile-first.
3. New payment, schedule, and user APIs live on staging, then production, passing end-to-end tests.
4. Deployment notes and a short Loom walkthrough so my in-house team can keep things running.

You will have direct access to our staging server, wp-cli, and a Slack channel with the ops team. Please outline relevant experience with high-traffic WordPress sites, complex WooCommerce or custom booking flows, and prior API work when you reply.