# System Architecture Interview

KYC = know your customer — it is a regulatory requirement for companies to do due diligence on who their customer is and, depending on how much they are transacting, have differing levels of verification and due diligence.

## Context
Users can have up to 4 documents:

ID front
ID back
Proof of address
Selfie
If all 4 documents are verified, user is verified else user is unverified.

User can resubmit for documents that have been rejected.

## Database Design
Design tables to store user documents

Custumer
- Id (pk, auto inc)
- Name (varchar)
- Email (varchar)

Kyc
- Id (pk, int, auto inc) 
- CustomerId (fk, int)
- Status (enum, Pending, Approved, Rejected)

KycDocuments
- Id (pk, int, auto inc)
- KycId (fk, int)
- DocumentUrl (varchar)
- DocumentType (enum, IdFront, IdBack, ProofOfAddress, Selfie)
- Status (enum, Pending, Approved, Rejected)
- SubmitDate (date time)

## API Endpoint Design
Design APIs for clients to query for user statuses
Design APIs for clients to submit user documents

- GET /customer/kyc -> get status
    Request Header:
        x-auth-token: "12345"
    Response Body:
    {
        "id": 123,
        "name": "cust name",
        "email": "[e-mail]",
        "kyc": {
            "status": "pending",
            "documents": [
            {
                "id": 1234,
                "document_type": "IdFront",
                "url": "https://s3.com/kyc/abcd/abcd123.jpg",
                "status": "pending",
                "submit_date": "2022-01-01T00:00:00"
            }
            ]
        }
    }
    Response code: 200 / 40x
    
- POST /customer/kyc/documents
    Desc: single api call upload only a single document
    Request Header:
        x-auth-token: "12345"
    Request Body:
    {
        "document_type": "IdBack",
        "data": "base64encodedstring"
    }
    Response code: 201 / 40x