Unit Technology Corporation
Signature Hub
Centralized digital signing platform
Backend Software Engineer · Team of 4 · banks and enterprises
The problem
Client systems needed one route to several signing providers without storing document content centrally.
Architecture
Simplified view, no client internals.
What I delivered
- Built backend services for signing through HSM, remote-signing providers, and VNeID.
- Worked on the event-driven signing flow across Spring Boot microservices on Kafka.
- Implemented PDF signing and validation (PAdES, PKCS#7) with HSM integration via PKCS#11.
Key decisions
Process signing asynchronously
Requests are published as events, processed asynchronously, and tracked by transaction code.
Keep sensitive content out of the hub
Request bodies between agent and hub are encrypted, and the data and audit services store metadata only.
Stack
Spring Cloud · Kafka · PostgreSQL · PKCS#11