Initiation and completion of an online transaction via a single user input action

A non-transitory computer readable medium that includes a set of instructions which, in response to execution by a processor of a computer system, cause the processor to perform a method of completing an online transaction that is performed via a user computing device connected to a merchant website via a web browser, the method comprising

• requesting a decryption key from a third-party key management service;
• encrypting payment method information with the decryption key;
• transmitting encrypted payment method information to a temporary storage location of a secure database;
• receiving at the processor a request to place an order on the merchant website;
• and
• in response to the request, instructing a headless browser that maintains a secure session with the merchant website to:
• request the decryption key from the third-party key management service and request the encrypted payment method information from the temporary storage location of the secure database, wherein the third-party key management service is different from the secure database;
• decrypt the encrypted payment method information with the decryption key;
• and
• after decrypting the encrypted payment method information, complete an online merchant checkout process for the merchant website using at least the payment method information.