Stopping off-platform deals with contact-swap detection

The problem

Marketplaces lose revenue when buyers and drivers swap phone numbers or emails in messages and finish the deal off-platform. Detection has to catch the evasion tricks without flagging legitimate conversations.

What I did

• Built and run the system that detects contact-info swapping in platform messages.
• For the latest upgrade, ran it silently against 174,000 real messages before launch.
• Fixed every case the old version had been missing before shipping.

The upgrade shipped after testing on 174,000 messages with zero new false positives.

The result

• The upgrade shipped after testing on 174,000 messages with zero new false positives.
• Every previously missed case found in testing was fixed before launch.
• The system runs in production, protecting on-platform revenue without flagging legitimate conversations.

Tools