Marketplaces implementation checklist

Ensure all transaction and payout API calls use unique idempotency keys to prevent duplicate charges or double-payouts during network retries.

Unit test the split-payment logic across different transaction sizes to ensure platform commissions and processing fees are calculated correctly before funds reach the seller.

Implement robust listeners for payment provider webhooks (e.g., payment_intent.succeeded, account.updated) with signature verification and 200-level response handling.

Verify that refunding a buyer correctly triggers a reversal of the seller's balance and, if applicable, the platform fee.

Integrate automated checks for seller identity verification and bank account validation to comply with AML regulations before enabling payouts.

Implement server-side validation to prevent XSS in reviews and integrate a profanity/spam filter for user-generated content.

Create a logic gate that programmatically applies 'Verified' status only after specific criteria (ID check, first successful sale) are met.

Build a reporting mechanism on listing and profile pages that flags content for admin review and triggers an automated notification to moderators.

Filter PII (emails, phone numbers) in pre-transaction messages if the business model requires preventing platform circumvention.

Log all administrative actions, including manual payout overrides, account bans, and listing deletions, with a timestamp and user ID.

Set up database triggers or webhooks to update the search index (e.g., Algolia) immediately when a listing's price, availability, or status changes.

Apply a temporary lock on inventory items when a user begins the checkout process to prevent overbooking or double-selling.

Test location-based filtering to ensure results are accurately sorted by distance and respect defined radius boundaries.

Implement fallback logic for zero-result queries, such as suggesting similar categories or expanding the search radius.

Use a CDN with auto-formatting (WebP) and resizing to ensure listing galleries do not degrade page performance or SEO.

Verify that buyers cannot access seller-specific API endpoints (e.g., payout settings) and sellers cannot modify other sellers' listings.

If support staff can 'log in as' a user, ensure this is restricted to specific roles and requires multi-factor authentication.

Implement middleware to redirect sellers to the onboarding flow if required profile fields or payment details are missing.

Configure shorter session durations for seller dashboards and sensitive financial pages compared to buyer browsing sessions.

If using third-party auth (Clerk/Supabase), ensure the JWT claims correctly reflect the user's marketplace role.

Automate immediate email delivery to both buyer and seller upon successful payment using a reliable provider like Resend.

Notify sellers via email or push notification when funds have been initiated for transfer to their bank account.

Implement SMS alerts for high-urgency actions like booking requests or last-minute cancellations.

Ensure marketing communications can be disabled while keeping critical transactional alerts (receipts, safety notices) active.

Verify that dynamic listing data and pricing tables render correctly across mobile and desktop email clients.