The build

Course platform issuing personalized completion certificates per cohort. Went from hand-run 9-hour batch to API-driven 8-minute parallel run.

Stack

· Rails
· Postgres
· Sidekiq
· Resend
· SnapPDF

Architecture

Ops used: /fill-form → /metadata → /protect

How they use SnapPDF

Proof Credential runs a cohort-based learning platform for mid-career professionals. Every six weeks, between 2,000 and 10,000 learners complete a program and expect a downloadable, personalized completion certificate with a unique credential ID that a future employer can verify.

The prior process: a part-time contractor at $45/hr ran a mail-merge in InDesign, exported to PDF, uploaded to their platform. A 3,000-person cohort took nine hours. A 10,000-person cohort broke InDesign and required them to chunk it manually.

The SnapPDF version runs as a Sidekiq job. For each graduate: fill the template with name + course + date + credential ID, stamp the credential ID into PDF metadata (so the verification page can read it back), protect with AES-256 to prevent editing. 20 parallel workers. 10,000 graduates → 8 minutes wall-clock.

Cost: ~$948/year (Pro plan) vs ~$16,200/year in contractor fees. The saving is only part of the win — graduates now receive their certificate within minutes of finishing the final module, not days. NPS jumped 12 points; the support team spent 70% less time on "where's my certificate" tickets.

The verification page is where metadata pays off. When a hiring manager uploads a candidate's certificate to Proof's verify page, the page reads the credential ID from PDF metadata, looks it up, displays "ISSUED 2026-04-12 · Valid" with the course details. No OCR, no QR-code scanning — the identifier is in the file itself.

Outcomes

Wall-clock time

9h → 8 min

Annual cost

$16,200 → $948

NPS

+12 points

Support tickets

–70%

Integration pattern

A simplified excerpt showing the core SnapPDF calls.

# app/jobs/issue_certificates_job.rb
class IssueCertificatesJob < ApplicationJob
  queue_as :certificates

  def perform(cohort_id)
    cohort = Cohort.find(cohort_id)
    snap = SnapPDF::Client.new(api_key: ENV['SNAPPDF_KEY'])

    cohort.graduates.find_each(batch_size: 100) do |grad|
      filled = snap.pdf.fill_form(
        file: cohort.template_url,
        values: {
          student_name: grad.display_name,
          course_title: cohort.program.title,
          completion_date: Date.today.iso8601,
          credential_id: grad.credential_id,
        },
        flatten: true
      )

      tagged = snap.pdf.set_metadata(
        file: filled.pdf,
        metadata: {
          title: "#{cohort.program.title} Certificate",
          subject: grad.credential_id,
          keywords: ['certificate', cohort.program.slug, grad.credential_id],
        }
      )

      locked = snap.pdf.protect(
        file: tagged.pdf,
        owner_password: Rails.application.credentials.cert_vault_key,
        encryption: 'aes-256'
      )

      CertMailer.with(graduate: grad, pdf: locked.pdf).issued.deliver_later
      grad.update!(certificate_issued_at: Time.current)
    end
  end
end

Start building like this

Free tier gives you 100 ops/month — enough to prototype any of the flows on this page. No card required.

Start free Read the quickstart Try in playground

Proof Credential