Kochab Labs · Fintech systems
PayFlow
A payment authorization system designed around deterministic mandates, durable provider operations, evidence integrity and fail-closed recovery paths.
PayFlow
System posture
Fail closed
Recovery
Durable + idempotent
Verification
Adversarial CI
Context
What the product had to solve
The problem
The constraint shaped the product.
Payment systems become dangerous when authorization, provider state and recovery logic disagree. The system needed to preserve one authoritative decision even across retries, ambiguous provider responses, crashes and reconciliation.
The system
Built around the critical path.
Kochab built the payment boundary as an auditable system rather than a collection of checkout screens: mandates define permission, decision receipts preserve authorization and the provider rail reconciles durable state without silently inventing a new attempt.
What we built
Product capability, not a feature dump.
01
Deterministic authorization and mandate fingerprinting
02
Decision receipts and evidence-chain integrity
03
Durable payment attempts and provider reconciliation
04
PayPal verification and idempotent recovery paths
05
Adversarial and PostgreSQL integration testing
System decisions
Why it was built this way
Decisions that carry the product.
- Authorization is computed before provider execution and cannot be weakened by retries.
- Ambiguous provider outcomes recover from durable state instead of creating another logical payment.
- Security-critical evidence is append-only and integrity checked.
- Crash, replay and concurrency behavior are treated as product requirements, not edge-case cleanup.
Technology
The stack follows the job.
TypeScript · PostgreSQL · PayPal · GitHub Actions