Code review and Quality assurance for development of Access control system

We are dealing with a vendor to develop an access control system for us and require a technical consultant to review the development and solution to affirm to us that the product is built as per our expectation and all contractual requirements have been delivered. Technology stack used for the system: Android - Kotlin or Flutter iOS - Swift 5.1+ Backend – Node JS Database - Mongo DB Front End - React JS Project Management Tool - Jira Server: AWS. Details about the access control system being developed for us: "Creation of a mobile app that can connect to 1000 smart locks in different locations with approximately 2000 users. The software should be device neutral and adding a new device should be relatively easy. The software should be quick in its response and should be scalable to at least 5 times the current defined capacity. The software shall be deployed on premises and will be accessed through a web application or mobile application (IOS and Android). We would also prefer the option for access to be offerred through SMS and use of a progressive web application instead of client having to download the mobile application. Information security is of key importance and therefore the infrastructure should be exceptionally difficult to infiltrate. All access rights will be predefined for set duration and all information captured will be sent to primary control center. Access will be granted through bluetooth or NFC for now, however, other hardware compatibility such as biometrics and RFID should also be possible. 3 layers will be constructed for this program: Top layer - Central command center will have access to all information and can control all access rights Middle layer - Access to limited information defined by the Central command center and will be able to control limited access rights. Client - Will only be allowed to access the premises defined by Top and middle layer."