A processor implemented method, further comprising: obtaining, via one or more hardware processors, a user request pertaining to a workflow execution in a serverless computing system, wherein a workflow is a sequence of a plurality of functions in a specific order; encoding, via the one or more hardware processors, a user role and a function execution sequence extracted from the user request to generate an encoded request; invoking, via the one or more hardware processors, execution of a function at a point of ingress, if a first level validation of the encoded request is successful; performing, via the one or more hardware processors, a second level validation of the encoded request, at each of a plurality of critical intermediate function calls of the serverless computing system to which access is requested post execution of the function at the point of ingress; and invoking, via the one or more hardware processors, a function execution at each of the plurality of critical intermediate function calls, if the second level validation is successful, wherein the second level validation at each of the plurality of critical intermediate function calls comprises: generating an n-gram based on a) a previously invoked function, and b) a current function invocation request from the encoded request; computing a cryptographic function of the n-gram and a corresponding user role to generate a transformed n-gram; and comparing the transformed n-gram with a plurality of protected access policies stored in an authenticated data structure, wherein, the second level validation is determined as successful if the current function invocation request is permitted by one or more of the plurality of protected access policies, and the second level validation is determined as failure if the current function invocation request is not permitted by one or more of the plurality of protected access policies. obtaining, via one or more hardware processors, a user request pertaining to a workflow execution in a serverless computing system, wherein a workflow is a sequence of a plurality of functions in a specific order; encoding, via the one or more hardware processors, a user role and a function execution sequence extracted from the user request to generate an encoded request; invoking, via the one or more hardware processors, execution of a function at a point of ingress, if a first level validation of the encoded request is successful; performing, via the one or more hardware processors, a second level validation of the encoded request, at each of a plurality of critical intermediate function calls of the serverless computing system to which access is requested post execution of the function at the point of ingress; and invoking, via the one or more hardware processors, a function execution at each of the plurality of critical intermediate function calls, if the second level validation is successful, generating an n-gram based on a) a previously invoked function, and b) a current function invocation request from the encoded request; computing a cryptographic function of the n-gram and a corresponding user role to generate a transformed n-gram; and comparing the transformed n-gram with a plurality of protected access policies stored in an authenticated data structure, wherein, the second level validation is determined as successful if the current function invocation request is permitted by one or more of the plurality of protected access policies, and the second level validation is determined as failure if the current function invocation request is not permitted by one or more of the plurality of protected access policies.