Launch Ready API security Checklist for founder landing page: Ready for paid acquisition in marketplace products?.

Launch Ready API Security Checklist for founder landing page: Ready for paid acquisition in marketplace products?

"Ready" does not mean the page looks finished. For a founder landing page in a marketplace product, ready means paid traffic can hit it without exposing secrets, breaking tracking, or sending users into a dead end.

If I were self-assessing this before spending on ads, I would expect four things to be true: the page loads fast enough to convert, the domain and email stack are trusted, the deployment is production-safe, and any API touchpoints are locked down. For paid acquisition, I want LCP under 2.5s on mobile, zero exposed secrets in the repo or browser bundle, SPF/DKIM/DMARC passing, and no critical auth bypasses anywhere in the path from landing page to signup or lead capture.

For marketplace products, the risk is higher because you usually have multiple user types, more API surface area, and more ways to leak data or misroute traffic. A broken redirect, weak CORS policy, or sloppy webhook handler can waste ad spend and create support load before you even get your first 50 leads.

Quick Scorecard

| Check | Pass criteria | Why it matters | What breaks if it fails | |---|---|---|---| | HTTPS everywhere | All pages and subdomains force SSL with no mixed content | Trust and browser security | Form submissions fail, warnings hurt conversion | | DNS is clean | Domain resolves correctly with intended apex and www behavior | Avoids traffic loss and SEO confusion | Users land on wrong host or see downtime | | Email auth passes | SPF, DKIM, DMARC all pass for sending domain | Keeps outreach and verification emails out of spam | Signup emails fail or get filtered | | Secrets are not public | No API keys in code, logs, client bundles, or build output | Prevents account takeover and billing abuse | Attackers use your keys or access data | | CORS is restricted | Only approved origins can call APIs | Blocks cross-site abuse | Data leaks and unauthorized requests | | Auth is enforced server-side | Sensitive endpoints require valid auth and role checks | Stops bypass through front-end only checks | Anyone can read or mutate marketplace data | | Rate limits exist | Login, signup, contact forms, and APIs have throttling | Protects against abuse and cost spikes | Bot traffic burns budget and crashes endpoints | | Redirects are intentional | Old URLs map to correct destinations with 301s only where needed | Preserves SEO and campaign links | Broken ads, lost attribution, poor UX | | Monitoring is live | Uptime alerts plus error tracking on deploy day one | Finds failures before customers do | You learn about outages from users | | Performance is acceptable | Mobile LCP under 2.5s and INP stays responsive | Paid traffic converts better on fast pages | Higher bounce rate and wasted ad spend |

The Checks I Would Run First

1. Check SSL and mixed content

• Signal: The site loads only over HTTPS, with no browser security warnings.
• Tool or method: Open the site in Chrome DevTools Security tab; run a crawl with Screaming Frog or similar; inspect console for mixed-content errors.
• Fix path: Force HTTPS at the edge with Cloudflare or your host, update hardcoded asset URLs to `https://`, then test every form submission flow again.

2. Check DNS behavior for apex, www, email, and subdomains

• Signal: `example.com`, `www.example.com`, app subdomains, and mail-related records resolve exactly as intended.
• Tool or method: Use `dig`, MXToolbox, or Cloudflare DNS dashboard.
• Fix path: Set one canonical domain strategy. I usually pick either apex -> www or www -> apex, then add 301 redirects everywhere else so ads do not split traffic.

3. Check secrets exposure

• Signal: No API keys appear in Git history, frontend bundles, environment previews, logs, or public config files.
• Tool or method: Search repo history plus build artifacts; run secret scanners like Gitleaks or TruffleHog; inspect browser sources.
• Fix path: Rotate any exposed keys immediately. Move all sensitive values to server-side environment variables and use least-privilege tokens only.

4. Check CORS and auth boundaries

• Signal: Only approved origins can call your APIs; protected endpoints reject unauthenticated requests with proper status codes.
• Tool or method: Send manual requests from an unapproved origin using curl/Postman; test preflight responses; verify role-based access by user type.
• Fix path: Lock CORS to exact origins. Enforce authorization on the server for every sensitive route instead of trusting UI state.

5. Check email deliverability

• Signal: SPF passes, DKIM signs outbound mail, DMARC policy is set correctly for your domain.
• Tool or method: Use MXToolbox or Google Postmaster Tools if available; send test messages to Gmail and Outlook.
• Fix path: Configure DNS records correctly before launch. If email is part of signup or verification, bad deliverability will quietly kill activation rates.

6. Check monitoring before traffic starts

• Signal: Uptime alerts fire within minutes of failure; error tracking captures frontend and backend exceptions.
• Tool or method: Set up UptimeRobot/Better Stack/StatusCake plus Sentry before campaigns go live.
• Fix path: Add alerting for homepage downtime, API errors, webhook failures, and login errors. If you cannot detect failure quickly, you cannot safely buy traffic.

## Example hardening pattern
Content-Security-Policy: default-src 'self'; connect-src 'self' https://api.yourdomain.com
Strict-Transport-Security: max-age=31536000; includeSubDomains

That snippet does not solve everything by itself. It does show the kind of edge hardening I want in place before paid acquisition starts sending strangers to your site.

Red Flags That Need a Senior Engineer

1. Your landing page talks to production APIs directly from the browser

• That often means exposed keys risk too much trust in client-side code.

2. You have multiple subdomains but no clear redirect strategy

• This creates broken links across ads, email links, app routes, and marketing pages.

3. You are unsure whether any secrets were ever committed

• If you cannot answer that quickly with evidence from scanning tools and history review,

you need cleanup before launch.

4. Your marketplace has role-based access but no server-side authorization audit

• Marketplaces fail here often because buyers see seller data or sellers see admin-only actions.

5. You plan to scale spend before monitoring exists

• If a payment form breaks at 9 pm Friday,

DIY Fixes You Can Do Today

1. Turn on Cloudflare proxying for the main domain

• This gives you SSL at the edge plus basic DDoS protection quickly.

2. Audit your forms and buttons for dead ends

• Every CTA should go somewhere real:

demo booking, waitlist, contact form, signup, or checkout.

3. Rotate any key that was copied into chat tools

• If an API key has been pasted into AI tools,

assume it is compromised until proven otherwise.

4. Set SPF now

• Even partial email authentication is better than none while you wait on full DKIM/DMARC setup.

5. Test mobile speed on a real device

• If your hero image,

third-party scripts, or video embed pushes LCP beyond 2.5s, remove them before buying clicks.

Where Cyprian Takes Over

If these checks fail, I would map them directly into Launch Ready so you are not trying to patch infrastructure while running ads.

| Failure area | What I fix in Launch Ready | Timeline | |---|---|---| | Domain confusion / bad redirects | DNS cleanup, canonical redirects, subdomain routing, and host normalization | Hours 1-8 | | Weak trust layer / SSL issues | Cloudflare setup, SSL enforcement, HSTS, and caching rules | Hours 1-12 | | Email deliverability problems | SPF/DKIM/DMARC configuration and validation tests | Hours 6-16 | | Secret exposure risk | Environment variable cleanup, secret rotation guidance, and deployment hardening | Hours 8-20 | | Production deployment instability | Safe deploy setup, rollback readiness, and handover checklist for release control | Hours 12-28 | | No observability / blind launch risk | Uptime monitoring, error tracking hooks, and alert routing setup before traffic starts flowing again later today? Actually no: before launch day ends? Wait let's keep concise.| Hours 18-36 |

For marketplace products specifically, I look at the API boundary first because that is where customer data leaks happen fastest. Then I verify deployment settings, monitoring, and handover so your team can keep shipping without reopening security holes every time a change goes live.

That makes sense when the problem is not "build me a whole product" but "make this one production-safe enough to buy traffic now."

What you get:

• DNS setup
• Redirects
• Subdomains
• Cloudflare configuration
• SSL enforcement
• Caching rules
• DDoS protection
• SPF/DKIM/DMARC setup
• Production deployment
• Environment variables review
• Secrets handling cleanup
• Uptime monitoring
• Handover checklist

My recommendation is simple: if your landing page already converts in tests but fails any of the security or delivery checks above, do not scale ads yet. Fix launch readiness first, then spend money on acquisition once the funnel can survive real traffic.

Delivery Map

References

• https://roadmap.sh/api-security-best-practices
• https://roadmap.sh/cyber-security
• https://roadmap.sh/frontend-performance-best-practices
• https://developer.mozilla.org/en-US/docs/Web/Security/HTTP_strict_transport_security
• https://www.cloudflare.com/learning/security/glossary/dns-records/

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Take the next step

If this is a problem in your product right now, here is what to do next:

• [Use the free Cyprian tools](/tools) - estimate cost, score app risk, check launch readiness, or pick the right service sprint.

• [Book a discovery call](/contact) - I will tell you honestly whether you need a sprint or if you can DIY the next step.

*Written by Cyprian Tinashe Aarons - senior full-stack and AI engineer helping founders rescue, launch, automate, and scale AI-built products.*