API Gateway: API Gateway Service

An API Gateway is an infrastructure component that serves as the single entry point for all Application Programming Interface (API) requests to a backend system. In the EUDI Wallet ecosystem, the API Gateway sits between the wallet applications (running on citizens' smartphones) and the backend microservices that handle credential issuance, status verification, trust registry queries, and other operations. The gateway routes each incoming request to the appropriate backend service while enforcing security policies, rate limits, authentication checks, and request validation.

The API Gateway performs several critical functions for EUDI Wallet backends. Request routing directs incoming API calls to the correct microservice based on the URL path, HTTP method, and request headers. A credential issuance request is routed to the issuance service, a revocation status check goes to the status service, and a trust registry query goes to the trust service. This routing is transparent to the wallet app, which communicates only with the gateway.

Authentication and authorization verification ensures that every request comes from a legitimate, authenticated source. The gateway validates OAuth 2.0 access tokens, checks client certificates for machine-to-machine communication, and verifies that the requesting entity has permission to access the requested resource. For the EUDI Wallet ecosystem, this includes verifying that credential issuers are registered in the trust framework and that relying parties are authorized to request specific credential types.

Rate limiting and throttling protect backend services from abuse and denial-of-service attacks. The gateway enforces per-client, per-endpoint, and global rate limits, ensuring that no single wallet instance or relying party can overwhelm the system. This is particularly important for EUDI Wallet services that must maintain high availability for hundreds of millions of potential EU citizens.

The API Gateway is the first line of defense for EUDI Wallet backend services. It terminates TLS connections, ensuring that all communication between wallet apps and the backend is encrypted. The gateway enforces minimum TLS version requirements (TLS 1.3 for EUDI Wallet services) and restricts cipher suites to those approved by national cybersecurity agencies like BSI and ANSSI.

Request validation at the gateway prevents malformed or malicious requests from reaching internal services. The gateway validates request body schemas, checks content type headers, enforces maximum request size limits, and sanitizes input parameters. For credential issuance endpoints, the gateway verifies that the request format complies with the OpenID for Verifiable Credential Issuance (OID4VCI) specification.

The gateway also implements complete logging and audit trails for all API interactions. Every credential issuance request, status check, and trust registry query is logged with metadata (timestamp, client identity, endpoint, response code) but without sensitive credential data. These audit logs support regulatory compliance, security monitoring, and incident investigation.

EUDI Wallet API Gateways must support extremely high availability targets, as digital identity services are critical infrastructure that citizens depend on for government services, financial transactions, and cross-border travel. Deployments typically use multiple gateway instances distributed across geographic regions and availability zones, with automatic failover ensuring continuity even if individual instances fail.

Load balancing distributes incoming requests across gateway instances based on health checks, response times, and geographic proximity. For cross-border scenarios where a French citizen uses their wallet in Germany, the gateway infrastructure must handle requests with low latency regardless of the user's location. CDN (Content Delivery Network) integration and anycast routing help minimize latency across the European continent.

The gateway layer also enables independent scaling of backend services. During high-demand periods, such as when a member state launches a new credential type, the issuance service can be scaled up independently while the status checking service continues at normal capacity. The API Gateway handles the routing smoothly, making this scaling transparent to wallet applications.