Notes on hiring, security, and how we build Kit.
Learn the current KSeF API rate limits, how rolling windows work, and how to retry 429 responses without duplicating invoice submissions in production.
Diagnose KSeF FA(3) validation errors by separating XML, semantic, duplicate, authentication, and transport failures, then retrying safely in production.
Compare KSeF TEST, DEMO, and PRD trust, data, API-version, and legal-effect boundaries, then promote an integration without leaking invoice data.
Implement KSeF 2.0 authentication with certificates, XAdES, access and refresh tokens, least-privilege permissions, and a safe 2027 migration plan.
Build a reliable KSeF UPO API flow: poll invoice status, handle terminal failures, verify the UPO XML, and archive durable acceptance evidence.
Greenhouse, Teamtailor, and SmartRecruiters all shipped the same class of feature in 2026. Here is what the ATS market is really converging on, and how to buy.
Cut application time to five minutes and conversion climbs up to 365%. We swapped candidate passwords for magic links. Here is the data behind it.