A method and system for signing a digital certificate in real time for accessing a service application hosted within a service provider (SP) computer system through an open application programming interface (API) platform is provided. The API platform is in communication with a memory device. The method includes receiving registration data from a developer computer device wherein the developer computer device is associated with a developer and configured to store a developer application, receiving a certificate signing request (CSR) from the developer computer device wherein the CSR includes a public key associated with the developer, verifying the registration data as being associated with the developer, signing the CSR to produce a signed certificate after verifying the registration data wherein the verifying and signing steps are performed by the SP computer system in real time, and transmitting the signed certificate and a client ID to the developer computer device.