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Fintech / Developer tools
FakePE
API sandbox enabling developers to test edge-case payment flows.
15x
Test Speedup
40+
Edge Cases Covered
-75%
Integration Bugs
fakepe.velnix.studio
Trigger Mock Error State
Incoming Webhook trace
16:49:15 [POST] /v1/charge_webhook → Status 402 Declined (Retry 1/3)
{ "id": "ch_98", "amount": 10000, "status": "failed", "error": "card_declined" }
Overview
FakePE simulates credit card processing behaviors and network events. It allows engineering teams to trigger bank declines, webhooks, and rate-limits programmatically to build bulletproof transaction loops.
The Stack
ReactTypeScriptGoPostgreSQLRedis WebhooksDocker Compose
What We Shipped
Custom error header-driven simulation API
WebSocket-based webhook dispatcher & retry logs
Interactive response console dashboard
API request trace explorer
The Challenge
Production sandboxes are slow, rigid, and make testing error states hard. Simulating a transient network timeout or a specific card decline requires editing backend mock rules repeatedly.
Our Solution
We built a mocking gateway where developers specify desired HTTP error states via headers. We accompanied this with a visual console showing live logs, request bodies, and outgoing webhooks.
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