Global Junior is a secure, microservices-based child banking app built with gRPC, Node.js, Docker, and Kubernetes, offering parental controls, tasks, savings, and smart spending.
— Two people with different permissions over the same money. The child spends, the parent sets the boundary, and the backend referees — neither client is trusted with the rules.
A child banking product has an unusual shape: the account holder and the account controller are different people with different permissions over the same money. The child spends; the parent sets the boundaries. Both need their own view, and the backend has to enforce the relationship rather than trust either client.
Controls are enforced server-side, which is the only place they mean anything. A limit that lives in the mobile app is a suggestion — the rule has to hold at the service boundary regardless of what the client sends.
Tasks, savings goals, and smart spending turn the account into something closer to a teaching tool than a wallet. Each is a small piece of product logic, and keeping them in their own services meant they could evolve without touching the core ledger path.
A spend attempt past the parent's daily limit, denied at the service boundary. This deny is the feature: a limit that lived in the mobile app would be a suggestion.
grpcurl — spend authorization. Request: grpcurl -d '{ "child": "acct_7031", "merchant": "GameZone", "amount": "1,500.00" }' junior.internal:443 \ junior.v1.SpendAuthz/Authorize. Response: { "decision": "DENIED", "rule": "DAILY_LIMIT", "limit": "1,000.00", "spent_today": "850.00", "set_by": "parent", "enforced_at": "service boundary" } 7 PERMISSION_DENIED · the rule held, whatever the client sent
Built With
Next Project