Technical guides from the engineers building Firsty.
From OAuth token to first eSIM activated, with QR code generation server-side. Real code, real credentials, real eSIM, in about 30 minutes.
Token caching, refresh strategy, and the security mistakes we see in production integrations every week.
A case study on how the cryptowallet Pexx integrated the Firsty API to launch loyalty-driven free data for their users in under three months.
What the LPA format actually is, how to render QR codes from it correctly, and why some QR codes work on iPhone but not Android.
Bundled provisioning APIs feel simpler. They are worse in production. Here is why separating eSIM creation from package ordering matters.
Exponential backoff, idempotency keys, and how to design a queue that survives partial failures.
A complete blueprint for building a travel eSIM business: database schema, pricing strategy, activation UX, and what to skip in v1.
Three identifiers, three meanings, frequently confused. Here is which one to use where.