How I'd build Email Marketing AI
I'd reach for Next.js on the frontend, FastAPI for the backend, Postgres for data, Stripe for billing, and Resend for email delivery. I'd use Claude API for the core email-generation feature, plus a lightweight job queue with Bull for async subject-line A/B testing. Rough estimate: 320 hours to production. That's about six weeks at 50 hours per week, or four weeks sprint-focused with some overlap. The GTM and initial customer onboarding layers push it closer to 380 hours if we're handling the Product Hunt launch ourselves.
Day-by-day plan
Day 1-2: Multi-tenant auth schema in Postgres, Next.js middleware for route protection, Stripe customer setup on signup. Day 3: Build the email-generation prompt, wire Claude API, test latency and token costs at scale. Day 4-5: Create the onboarding flow - connect LinkedIn or Apollo data source, map fields, build the email template builder UI. Day 6-7: Stripe webhook integration for subscription state, self-serve tier logic (free trial limits, paid tiers), invoice delivery via Resend. Week 2: Subject-line A/B testing framework with Bull, analytics dashboard showing open rates pulled from Resend webhooks, first retention hook - CRM sync scaffolding. Week 3: Product Hunt launch assets, SEO content for cold email subject-line queries, customer success playbook. Week 4: Monitoring, observability, pager on-call runbook, final polish based on early user feedback.
What's hard about this build
The data-integration layer is messier than it looks. Apollo and Instantly both let you export contacts, but schema variance across customers kills naive bulk-import logic - name fields, company structure, custom attributes all shift. I'd validate and normalize on ingest, but that's 30-40 hours of edge-case handling. Second: deliverability. Resend is solid for transactional mail, but cold email campaigns need DMARC/SPF/DKIM alignment on customer domains, and Gmail and Outlook are aggressive about filtering bulk mail. I'd need to build a warning layer and educate users that the product can't overcome their sender reputation. Third: the churn dynamic is brutal in this space. Customers chase open rates and deliverability like it's a magic lever, then blame the tool and churn after 60 days. I'd need strong enough retention hooks - send tracking, domain reputation scoring, CRM sync - to justify stickiness, and I'd build that infrastructure early or risk 80% annual churn.
What's fast because of AI
Claude API compresses the email-generation engine. Prompting takes 8 hours; iterating on tone, personalization depth, and edge cases around long company names or jargon normally takes another 15-20. With Claude, I can iterate in real time with the customer, and I ship better prompts in parallel with the rest of the product. Scaffolding the Next.js and FastAPI boilerplate is 60-80 hours normally; Claude cuts that to 30 by generating 80% of the middleware, form validation, and test structure. I still review and refine, but the time compression is real. For the analytics dashboard, enumeration of edge cases - timezone handling, retry logic for Resend webhooks, state-machine logic for multi-step onboarding - Claude surfaces 90% of the gotchas in a single prompt. Copywriting for the product UI and landing page normally takes 20-30 hours with iteration; Claude drafts product-voice copy in 3-4 hours, and I refine for tone. I'd say AI shaves 80-100 hours off a typical 320-hour build, mostly in scaffolding and copy.
How I'd hand it off
I'd ship a 20-minute Loom walkthrough covering the admin dashboard, API key management, and the core user workflow from contact import to send. I'd write a runbook in Linear: deployment steps, Stripe webhook monitoring, Resend API health checks, common support flows. I'd run a 30-day on-call rotation with you - any production issues, I'm the first responder; after 30 days, I'd hand off documentation and escalation paths. All credentials transfer to your AWS account via a private pass-manager export. I'd leave you with a monitoring dashboard in Datadog or Posthog so you can track adoption, churn cohorts, and API latency yourself. By day 30, you should be able to operate this without me, but I'd be one Slack message away if things break.