E-signature platform with its own SDK
A digital signature platform built as a standalone product: Next.js backend, versioned React SDK and cryptographic sealing to ETSI CAdES with RFC 3161 timestamping.
POST /v1/documents 201
POST /v1/documents/:id/send
recipients 2 · sequential
✓ signed 1/2 ✓ 2/2
⇡ webhook document.completed 200
CAdES
ETSI-compliant sealing
SDK
published React package
3.1
OpenAPI as source of truth
Starting point
The second product we built with LohnLab: for document workflows with digital signatures, the team needed its own e-signature solution - flexible enough to be embedded into several products instead of being tied to an external provider.
Approach
We built the platform as an API product with its own SDK: a Next.js backend for documents, signing flows, templates and webhooks - plus a headless React SDK whose types are generated from the OpenAPI specification. CI enforces it: if the SDK drifts from the spec, the release fails.
Result
PDF upload, field placement, sequential and parallel signing, ETSI CAdES sealing from a P12 certificate with timestamping and long-term validation, audit trails and HMAC-signed webhooks - a product any LohnLab frontend can embed through the SDK.
$git log --graph
mainnext: your-product
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