How We Built Pledge Now, Pay Later: Architecture, Decisions & Lessons

PledgeNow started as a simple idea: let charity event attendees pledge donations and pay later. What we built is a full autonomous donation infrastructure — and this is how we did it.

The Problem

At charity fundraising events — galas, iftars, dinners — there's a moment of peak generosity. The speaker finishes, the video plays, people are moved to give. But:

• Most people don't carry cash
• Card machines are slow and create queues
• The moment of inspiration passes
• Charities lose 40-60% of pledged donations to the Pledge Gap

We needed a system that captures the pledge in the moment and then automates everything afterwards — reminders, payments, Gift Aid, reporting.

Architecture Overview

Frontend (Next.js 14)        Donor-facing pledge flow
    |                        Campaign pages, QR codes
    v
API Routes (Next.js)          Business logic, auth
    |                        Pledge creation, payment links
    v
Postgres 16                  Pledges, orgs, campaigns, events
    |                        Gift Aid declarations, payment status
    v
Stripe                       Payment processing
    |                        Payment intents, webhooks
    v
AI Steward                   Natural language interface
    |                        13 tools, contextual responses
    v
WhatsApp (WAHA)             Donor comms, reminders
                              Nudge sequences, status updates

Key Technology Decisions

Next.js 14 (App Router)

We chose Next.js for the full-stack capability — server components, API routes, and static generation in one framework. The App Router's server actions handle form submissions without client-side JavaScript for the critical pledge flow.

Why not a SPA + separate API? For a tool used at events, we need fast initial loads and progressive enhancement. Server-rendered HTML works when JavaScript fails. SPAs don't.

Postgres (not MySQL, not MongoDB)

Relational data model is essential for financial data. Pledges have relationships to donors, campaigns, organisations, and payments. Postgres gives us:

• ACID transactions (critical for payment processing)
• JSON columns for flexible metadata
• Prisma ORM for type-safe queries
• Full-text search for the AI steward

Stripe (not GoCardless, not PayPal)

Stripe gives us Payment Links, Payment Intents, and webhooks that let us create a seamless pay-later flow. Donor pledges at an event, receives a payment link via WhatsApp/email, pays when ready.

AI Steward (not a chatbot)

The AI Steward is an internal tool for charity administrators. It answers questions like "How much did we raise at last Friday's dinner?" or "Send a nudge to donors who haven't paid from the gala."

Built on OpenAI's GPT-4.1-nano (fast, cheap, sufficient) with 13 custom tools:

• Query pledges by campaign, date, status
• Generate stats grids and visual cards
• Draft WhatsApp nudge messages
• Check payment status across donors
• Create campaign summaries

The steward never says "I'm an AI." It speaks as the charity's operations assistant.

Infrastructure: One Server, Six Products

Everything runs on a single dedicated server (64GB RAM, 8 cores) using:

• Incus — lightweight containers (LXD successor)
• Docker — application containers within each Incus container
• Traefik — reverse proxy, automatic SSL, routing
• Dokploy — deployment management

Total monthly cost: ~£40. We run PledgeNow, QuikCue site, JustVitamin, two Ghost blogs, Gitea, and multiple other services on this single box.

Why not AWS/Vercel/Railway? Control and cost. At our scale, managed cloud would cost 10-20x more and give us less flexibility. We can deploy in seconds, debug directly, and own our infrastructure.

Lessons Learned

1. The pledge-to-payment conversion is everything

A pledge is worthless until it converts to a payment. Our entire UX and automation is optimised for this single metric. Automated reminders at 24h, 72h, and 7 days post-pledge lifted conversion from ~55% to ~80%.

2. WhatsApp beats email for donor communications

Open rates: WhatsApp 90%+, Email 15-25%. For time-sensitive payment reminders, WhatsApp is the only channel that works.

3. Charities need less software, not more

Every feature we didn't build was a good decision. Charities are overwhelmed by tools. PledgeNow does one thing — pledge collection — and does it without requiring any technical knowledge to operate.

4. Self-hosting is a superpower

When something breaks at 2am before a charity's biggest event, we SSH in and fix it in minutes. No support tickets, no waiting for a provider's SLA. This speed has saved multiple events.

What's Next

We're building toward a fully autonomous charity operations stack — where donations flow from event to bank account to Gift Aid claim to thank-you message without human intervention. PledgeNow is the first piece.

If you're building for the charity sector and want to discuss architecture, infrastructure, or approach — reach out. We're always happy to talk shop.