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🚪 API Gateway In Modern Systems

The API Gateway acts as the central entry point into distributed systems within the ConnectSoft platform. It routes client requests to appropriate backend services, handles authentication and tenant resolution, and applies essential cross-cutting concerns such as logging, rate limiting, observability, and security enforcement.

Info

In ConnectSoft, the API Gateway is a dedicated standalone solution template.
It is not based on YARP or Envoy, but rather a custom-coded .NET Core gateway, designed from the ground up to support multi-tenant SaaS platforms, enterprise service boundaries, and AI-ready ecosystems.
There are additional templates based on YARP and Envoy, but they are not the focus of this document.

It is a self-contained reverse proxy that supports routing, policy injection, JWT validation, observability, and more — all baked in.

🧭 Overview

Modern microservices and SaaS platforms require a layer of indirection between public clients and internal service implementations.
The API Gateway pattern solves this by acting as a façade that centralizes external access and applies reusable middleware logic — improving maintainability, security, and runtime transparency.

The ConnectSoft API Gateway provides:

  • ✅ Centralized routing for REST and gRPC services
  • 🔐 Authentication and multi-tenant authorization
  • 🔄 Request transformation and header rewriting
  • 📊 Observability via OpenTelemetry and Serilog
  • 📈 Rate limiting and circuit breaker patterns
  • 🧠 Custom logic injection via middleware pipeline

🔍 Why It Matters

Without a gateway, client applications must:

  • Know the address of every microservice
  • Handle authorization and rate limits independently
  • Replicate error handling, health checks, and retry logic
  • Be tightly coupled to the backend architecture

The ConnectSoft API Gateway decouples all of this with a unified, programmable interface.

Concern Without Gateway With ConnectSoft Gateway
Authentication Implemented separately per service Centralized via JWT/OIDC
Rate Limiting Difficult to coordinate Built-in and configurable
Routing Static URLs or hardcoded service discovery Dynamic config or service discovery-aware
TLS Termination Per-service certificates Central TLS at the gateway
Observability Fragmented across services Unified via tracing, metrics, and logs
Multi-Tenancy Spread across services Enforced via tenant-aware policies and guards

🧱 Position in Architecture

The gateway is deployed at the edge of the system, interfacing with clients, internal APIs, and identity infrastructure.

graph TD
    Client["User / Mobile / Bot"] --> Gateway["API Gateway (Custom Template)"]
    Gateway --> AuthService["Identity Service"]
    Gateway --> ProductService["Product Service"]
    Gateway --> OrderService["Order Service"]
    Gateway --> NotificationService["Notification Service"]
    Gateway --> Observability["OpenTelemetry / Serilog / Metrics"]
Hold "Alt" / "Option" to enable pan & zoom

Tip

The ConnectSoft gateway is multi-protocol. It can route HTTP/REST, gRPC, and websocket requests, and integrates with upstream services via direct endpoints or service discovery (in Kubernetes or container platforms).

🧰 Core Technology

Component Purpose
.NET Core Gateway App Fully custom, extensible reverse proxy
Built-in Middleware Routing, auth, tenant filters, tracing, logging
OpenTelemetry Distributed tracing + metrics export
Serilog Structured JSON logging with tenant-aware enrichment
Pulumi or Terraform Deployment via infrastructure-as-code
Docker/Kubernetes Containerized and scalable deployment ready

🚀 Gateway Template Highlights

  • Comes pre-wired with:
  • RequestRoutingMiddleware
  • JwtValidationMiddleware
  • TenantContextResolver
  • ObservabilityEnricherMiddleware
  • CorrelationIdHandler
  • Designed to work with ConnectSoft microservices, OpenIddict-based auth, and message brokers.

🔄 Core Responsibilities of the API Gateway

The ConnectSoft API Gateway is more than just a traffic router — it applies centralized logic to manage requests, enforce contracts, and direct traffic with resilience and intelligence.

🧭 Key Functional Areas

Feature Area Responsibility
Routing Direct traffic to backend services via path, host, header, or method rules
Request Transformation Modify headers, paths, or payloads for compatibility or security
Load Balancing Distribute requests across service replicas
Service Aggregation Combine multiple backend responses into one (for façade APIs)
Fallback / Retry Handle failures gracefully with retry/circuit breaker patterns
Protocol Bridging Route between REST, gRPC, WebSocket, and event-driven systems

🚦 Dynamic Routing

The gateway supports path-based, host-based, and header-based routing rules.

app.UseEndpoints(endpoints =>
{
    endpoints.MapReverseProxy(proxyPipeline =>
    {
        proxyPipeline.Use((context, next) =>
        {
            var route = RouteResolver.Resolve(context);
            context.Items["UpstreamRoute"] = route;
            return next(context);
        });

        proxyPipeline.UseMiddleware<AuthenticationMiddleware>();
        proxyPipeline.UseMiddleware<TenantContextMiddleware>();
        proxyPipeline.UseMiddleware<ObservabilityEnricherMiddleware>();
    });
});

Example: Path-Based Routing Logic 

if (path.StartsWith("/api/products"))
    return "product-service";
else if (path.StartsWith("/api/orders"))
    return "order-service";


graph TD
    Client --> Gateway
    Gateway -->|/api/products/*| ProductService
    Gateway -->|/api/orders/*| OrderService
Hold "Alt" / "Option" to enable pan & zoom

Tip

Routing can also support subdomain-based separation or multi-versioning via query, headers, or path segments.

🔁 Request and Response Transformation

The gateway enables centralized transformation of:

  • 🔀 Paths: Rewriting /api/v1/products → /products
  • 🪪 Headers: Injecting X-Tenant-Id, X-Correlation-Id, or removing sensitive headers
  • 🔁 Payloads: Optional rewriting (e.g., to comply with backend schema)
context.Request.Headers["X-Tenant-Id"] = tenantContext.TenantId;
context.Response.OnStarting(() =>
{
    context.Response.Headers["X-Processed-By"] = "ConnectSoft Gateway";
    return Task.CompletedTask;
});

Info

Centralized transformation logic reduces duplication and keeps backend services lean and focused on business logic.

⚖️ Load Balancing & Resilience

When routing to internal services, the gateway supports:

  • Weighted round-robin or random selection
  • Integration with service registries (via abstraction)
  • Passive health check fallback (e.g., service instance unavailability)
graph TD
    Gateway -->|LB| ProductServiceA
    Gateway -->|LB| ProductServiceB
Hold "Alt" / "Option" to enable pan & zoom 
var upstreams = _serviceRegistry.GetHealthyInstances("order-service");
var target = _loadBalancer.Select(upstreams);
context.ForwardTo(target);

Tip

Load balancing logic is pluggable and tenant-aware. You can implement custom strategies based on user tier, edition, or SLA.

🧩 Service Composition (Facade APIs)

For complex clients (e.g., mobile apps), the gateway can:

  • Compose multiple service calls into one aggregated response
  • Apply custom shaping for frontend needs

Example: Compose User Profile

var user = await _userService.GetUser(id);
var subscriptions = await _subscriptionService.GetByUser(id);
return new UserProfileDto(user, subscriptions);

graph TD
    Client --> Gateway
    Gateway --> UserService
    Gateway --> SubscriptionService
    Gateway -->|Aggregates| Client
Hold "Alt" / "Option" to enable pan & zoom

Warning

Use composition sparingly — gateways should avoid becoming brittle or violating service boundaries. Favor BFF (Backend for Frontend) patterns for tightly coupled UIs.

💡 Best Practices

Practice Description
✅ Keep routes versioned Use /v1/, /v2/ or headers to support evolution
✅ Inject correlation & tenant headers Enable observability and tenancy enforcement downstream
✅ Strip unsafe headers Remove headers like Authorization or X-Forwarded-For unless needed
✅ Compose smartly Avoid overloading gateway with complex business logic
✅ Prefer contracts over reflection Define routes and services explicitly in configs or middleware

🔐 Security and Access Control

Security is a core function of the API Gateway in any distributed architecture.
In ConnectSoft, the API Gateway acts as the primary security perimeter, enforcing identity, access, and tenant boundaries before any request reaches downstream services.

Info

The ConnectSoft Gateway is pre-integrated with OpenIddict (or other external OIDC providers), allowing seamless validation of access tokens and injection of tenant and identity context into the request pipeline.

🛡️ JWT Validation (OAuth2 / OIDC)

All external requests must include a valid bearer token. The gateway verifies:

  • Signature validity
  • Expiration (exp)
  • Audience (aud) and issuer (iss)
  • Required scopes and roles
  • Tenant claims

Example: JWT Middleware Extractor

services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.Authority = Configuration["Auth:Authority"];
        options.Audience = "connectsoft-api";
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidIssuer = "https://identity.connectsoft.io",
            RoleClaimType = "role",
            NameClaimType = "name"
        };
    });

Tip

Tokens can be issued via OpenIddict, Azure AD, Okta, or any compliant OIDC provider. The Gateway is fully pluggable.

🧩 Multi-Tenant Authorization

The ConnectSoft Gateway automatically resolves tenant context from:

  • Token claims (tenant_id)
  • Subdomain or header (x-tenant-id)
  • Route parameter or query string (fallback)
public class TenantContextMiddleware
{
    public async Task Invoke(HttpContext context, RequestDelegate next)
    {
        var tenantId = context.User.FindFirst("tenant_id")?.Value
            ?? context.Request.Headers["X-Tenant-Id"].FirstOrDefault();

        if (string.IsNullOrEmpty(tenantId))
            throw new UnauthorizedAccessException("Missing tenant context");

        context.Items["TenantContext"] = new TenantContext(tenantId);
        await next(context);
    }
}

Tenant context is then injected into:

  • X-Tenant-Id header to downstream services
  • Correlation IDs
  • Logs and OpenTelemetry spans

🔐 Scope & Role Enforcement

Requests are validated against required roles or scopes per route.

Example: Role/Scope Policy Enforcement

if (!context.User.IsInRole("admin") && !context.User.HasScope("orders:write"))
{
    context.Response.StatusCode = 403;
    await context.Response.WriteAsync("Forbidden");
    return;
}

Recommended Scope Format: - users:read, users:write - orders:read, orders:admin - tenant:manage, audit:view

# Declarative route metadata (optional future extension)
routes:
  - path: /api/orders
    requiredScopes:
      - orders:read
      - orders:write
    requiredRoles:
      - user
      - admin

🔄 Propagating Security Context

Once the request is validated, the gateway forwards:

  • X-User-Id
  • X-Tenant-Id
  • X-Scopes
  • X-Request-Id

This allows downstream services to make access decisions without revalidating tokens.

sequenceDiagram
    Client->>Gateway: Bearer Token
    Gateway->>AuthService: Token Validation
    AuthService-->>Gateway: Claims (userId, tenantId, scopes)
    Gateway->>ProductService: Forwarded request with headers
Hold "Alt" / "Option" to enable pan & zoom

🧼 Input Filtering & Header Sanitization

To prevent injection, spoofing, or header pollution:

  • ❌ Strip X-Forwarded-For, Authorization, Cookie unless explicitly whitelisted
  • ✅ Inject known headers under safe names (X-User-Id, X-Tenant-Id)
  • ✅ Reject unknown content types and large payloads
  • ✅ Use model binding + schema validation in downstream services

Example: Header Sanitizer Middleware

public async Task Invoke(HttpContext context, RequestDelegate next)
{
    var forbiddenHeaders = new[] { "Authorization", "Cookie", "X-Forwarded-For" };
    foreach (var h in forbiddenHeaders)
        context.Request.Headers.Remove(h);

    await next(context);
}

🛡️ Rate Limiting and Abuse Protection

Basic request throttling is built-in using an in-memory or distributed counter (Redis recommended).

Example: IP + Token Throttling

if (_rateLimiter.IsLimitExceeded(userId, path))
{
    context.Response.StatusCode = 429;
    await context.Response.WriteAsync("Rate limit exceeded");
    return;
}
Tier Limit
Free Tier 100 requests / 5 minutes
Paid Tier 1000 requests / 1 minute
Internal Bots Unlimited (token scoped)

Warning

Always throttle unauthenticated routes (e.g. /health, /public) by IP or subnet.

🔍 Auditing & Compliance

Every request through the gateway can be logged:

  • Endpoint, user, tenant
  • Correlation ID
  • IP, User-Agent, token fingerprint
  • Scope and authorization decision

Example: Serilog Template 

Log.ForContext("UserId", userId)
   .ForContext("TenantId", tenantId)
   .ForContext("Route", context.Request.Path)
   .Information("API request handled");

✅ Security Best Practices

Practice Description
✅ Use token expiration (short-lived JWTs) Avoid long-term credentials
✅ Strip unsafe headers Remove unknown or sensitive headers before forwarding
✅ Propagate trace and tenant headers Enable distributed observability and policy enforcement
✅ Validate request schema Use JSON Schema or typed DTOs to prevent injection
✅ Monitor auth failures Alert on spikes in 401 or 403 responses
✅ Encrypt traffic Use HTTPS + TLS 1.2+ termination at the edge

📊 Observability and Resilience

A production-grade API Gateway must do more than route traffic — it must enable full insight into system behavior and gracefully handle failures when things go wrong.

At ConnectSoft, the gateway provides built-in telemetry, resilience policies, health checks, and diagnostic propagation out of the box.

🧾 Structured Logging (Serilog)

All incoming and outgoing traffic is logged with:

  • Timestamp, method, route
  • Tenant ID, User ID (when authenticated)
  • Correlation ID (tracing)
  • Status code, latency, source IP
Log.ForContext("TenantId", tenantId)
   .ForContext("UserId", userId)
   .ForContext("RequestId", context.TraceIdentifier)
   .Information("Handled {Method} {Path}", method, path);

Logs are output in JSON format, ready for ingestion into:

  • Azure Monitor
  • Elastic Stack (Fluentd → Elasticsearch → Kibana)
  • Seq, Datadog, Grafana Loki

Tip

Every ConnectSoft template includes log enrichment for X-Tenant-Id, X-Correlation-Id, and operation context.

🕸️ Distributed Tracing (OpenTelemetry)

The gateway acts as a trace root for every request and propagates tracing headers downstream:

  • traceparent (W3C standard)
  • X-Request-ID
  • X-Correlation-ID
using var activity = _activitySource.StartActivity("Gateway Request", ActivityKind.Server);
activity?.SetTag("http.route", context.Request.Path);
activity?.SetTag("tenant.id", tenantId);
activity?.SetTag("user.id", userId);

sequenceDiagram
    participant Client
    participant Gateway
    participant OrderService
    participant BillingService

    Client->>Gateway: Request with trace headers
    Gateway->>OrderService: Forward with propagated traceparent
    OrderService->>BillingService: Downstream trace
Hold "Alt" / "Option" to enable pan & zoom

Traces are exported to:

  • Azure Application Insights
  • Jaeger
  • Zipkin
  • Tempo (Grafana)

📈 Metrics (Prometheus-compatible)

The gateway exposes /metrics for:

Metric Description
http_requests_total Count of requests per route/method
http_request_duration_seconds Histogram of request times
http_auth_failures_total Auth/authorization failure counts
http_tenant_resolution_failures Invalid or missing tenant errors 
_meter.CreateCounter<long>("http_requests_total")
      .Add(1, new Tag("route", context.Request.Path), new Tag("method", method));

Info

Metrics can be scraped by Prometheus, visualized in Grafana, and used for alerting and SLO tracking.

💓 Health Checks & Readiness

The gateway provides endpoints for:

  • /health – Liveness probe
  • /ready – Readiness for upstream services
app.MapHealthChecks("/health");
app.MapHealthChecks("/ready", new HealthCheckOptions
{
    Predicate = r => r.Tags.Contains("ready")
});

Upstream probes: The gateway checks the availability of critical dependencies (e.g., IdentityService, Redis, MetricsSink) and exposes status.

graph TD
  Gateway --> IdentityService
  Gateway --> RedisCache
  Gateway --> TelemetrySink
Hold "Alt" / "Option" to enable pan & zoom

Warning

Always tag readiness checks with ready so that Kubernetes or your orchestrator can gracefully drain connections on shutdown.

🔁 Retry & Circuit Breaker Policies

To protect against transient failures and overloaded services, the gateway includes:

  • ⏱ Retry on timeouts, 502/503/504
  • 🛑 Circuit breaker on repeated failures
  • 🔁 Exponential backoff with jitter

Example: Retry with Polly

var retryPolicy = Policy
    .Handle<Exception>()
    .WaitAndRetryAsync(new[]
    {
        TimeSpan.FromMilliseconds(100),
        TimeSpan.FromMilliseconds(250),
        TimeSpan.FromMilliseconds(500)
    });

Example: Circuit Breaker

var circuitBreaker = Policy
    .Handle<Exception>()
    .CircuitBreakerAsync(5, TimeSpan.FromSeconds(30));

Combined policy: 

var resiliencePolicy = Policy.WrapAsync(retryPolicy, circuitBreaker);
await resiliencePolicy.ExecuteAsync(() => _proxy.ForwardAsync(...));


graph TD
    Gateway --> RetryPolicy --> CircuitBreaker --> ProductService
Hold "Alt" / "Option" to enable pan & zoom

🔌 Graceful Degradation & Fallbacks

In the event of critical failures, fallback logic can be added:

try
{
    await _proxy.ForwardAsync(context);
}
catch (Exception ex)
{
    Log.Error(ex, "Upstream failure");
    context.Response.StatusCode = 503;
    await context.Response.WriteAsync("Service temporarily unavailable");
}

You can optionally:

  • Serve stale cache
  • Return synthetic response
  • Redirect to failover instance

✅ Best Practices for Observability and Resilience

Practice Description
✅ Always use correlation and trace IDs Required for debugging distributed transactions
✅ Collect Prometheus-compatible metrics Enables SLO monitoring and alerting
✅ Log in structured format Supports search, filtering, and analysis
✅ Retry idempotent calls only Avoid retrying unsafe POST/PUTs unless designed to tolerate it
✅ Use circuit breakers per backend Prevent cascading failure from a single service
✅ Expose liveness and readiness probes Required for container orchestration

🚀 Deployment and Extensibility

The ConnectSoft API Gateway is designed to be infrastructure-agnostic and easily deployed across:

  • ⛅ Cloud (Azure, AWS, GCP)
  • 🐳 Containerized environments (Docker, Kubernetes, AKS)
  • 🏢 On-premise or hybrid setups

Its extensibility model enables developers to inject custom middleware for authentication, tracing, tenant resolution, metrics, or business logic.

📁 Environment Configuration

The gateway supports layered configuration through:

  • appsettings.json
  • appsettings.{Environment}.json
  • Environment variables (e.g., Docker, Kubernetes ConfigMaps)
  • Secret injection (e.g., Azure Key Vault, HashiCorp Vault)

Example: Configuration Structure

/config
  appsettings.json
  appsettings.Development.json
  appsettings.Production.json
/secrets
  vault-secrets.json

Sample appsettings.Production.json

{
  "Auth": {
    "Authority": "https://identity.connectsoft.io",
    "Audience": "connectsoft-api"
  },
  "Observability": {
    "EnableTracing": true,
    "Exporter": "AzureMonitor"
  },
  "RateLimiting": {
    "Free": 100,
    "Paid": 1000
  }
}

🐳 Docker-Based Deployment

A prebuilt Dockerfile is provided in the gateway template:

FROM mcr.microsoft.com/dotnet/aspnet:8.0
WORKDIR /app
COPY . .
EXPOSE 5000
ENTRYPOINT ["dotnet", "ConnectSoft.Gateway.dll"]

Run locally:

docker build -t connectsoft-gateway .
docker run -e ASPNETCORE_ENVIRONMENT=Production -p 5000:5000 connectsoft-gateway

☸️ Kubernetes (AKS) Deployment

The gateway is Kubernetes-native, exposing liveness/readiness probes and supporting autoscaling.

Helm chart example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: connectsoft-gateway
spec:
  replicas: 3
  containers:
    - name: gateway
      image: registry/connectsoft-gateway:latest
      ports:
        - containerPort: 5000
      readinessProbe:
        httpGet:
          path: /ready
          port: 5000
      livenessProbe:
        httpGet:
          path: /health
          port: 5000

Horizontal scaling via HPA:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
spec:
  minReplicas: 2
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          averageUtilization: 70

⚙️ Pulumi (IaC)

Use Pulumi to automate infrastructure provisioning:

import * as k8s from "@pulumi/kubernetes";

const appLabels = { app: "gateway" };

const deployment = new k8s.apps.v1.Deployment("gateway", {
  spec: {
    selector: { matchLabels: appLabels },
    replicas: 3,
    template: {
      metadata: { labels: appLabels },
      spec: {
        containers: [{
          name: "gateway",
          image: "registry/connectsoft-gateway:latest",
          ports: [{ containerPort: 5000 }]
        }]
      }
    }
  }
});

Info

ConnectSoft's Pulumi automation includes gateway, microservices, observability stack, and ingress controller by default.

🧩 Custom Middleware Extensibility

The gateway’s internal pipeline supports middleware injection at any layer:

app.UseMiddleware<RequestRoutingMiddleware>();
app.UseMiddleware<JwtValidationMiddleware>();
app.UseMiddleware<TenantContextResolver>();
app.UseMiddleware<ObservabilityEnricherMiddleware>();

💡 Common Middleware Extensions

Use Case Middleware Class
Add headers (e.g. version) HeaderInjectionMiddleware
Geo-block traffic GeoRestrictionMiddleware
Dynamic A/B routing CanaryRoutingMiddleware
Multi-edition auth policy EditionGuardMiddleware
Request time limit RequestTimeoutMiddleware 
public class HeaderInjectionMiddleware
{
    public async Task Invoke(HttpContext context, RequestDelegate next)
    {
        context.Response.Headers.Add("X-Api-Version", "1.0");
        await next(context);
    }
}

🧪 CI/CD Integration

CI/CD-ready templates support:

  • ✅ Azure Pipelines (azure-pipelines.yml)
  • ✅ GitHub Actions (.github/workflows/deploy.yml)
  • ✅ Docker + Helm + Pulumi deploy stages
  • ✅ Pre-flight health checks + tracing verification

GitHub Actions sample:

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2
      - name: Build & Push
        run: |
          docker build -t connectsoft-gateway .
          docker push registry/connectsoft-gateway
      - name: Deploy via Pulumi
        run: pulumi up --yes

✅ Deployment Best Practices

Area Best Practice
Config Use appsettings.{env}.json and override with ENV vars or secret stores
Secrets Inject via Azure Key Vault or Kubernetes Secrets
Scale Enable HPA for autoscaling under high load
Rollback Tag releases; support Helm or Pulumi rollback
Monitoring Validate deploy success via /ready, /metrics, /trace
Automation Use CI pipelines for build/test/deploy

🧪 Real-World Use Cases and Patterns

The ConnectSoft API Gateway is used across a wide range of real-world architectures — from high-traffic SaaS platforms and e-commerce portals to AI orchestration and DevOps automation.

This section outlines patterns and applied examples of how the gateway operates in production environments.

🏢 SaaS Platform Gateway (Multi-Tenant)

Scenario: Serve thousands of tenants with isolated access policies and feature toggles.

Responsibilities: - Inject X-Tenant-Id based on token claim or subdomain - Enforce per-tenant feature access - Centralize observability and rate limits

sequenceDiagram
    participant Client
    participant Gateway
    participant IdentityService
    participant TenantService

    Client->>Gateway: Request with Bearer Token
    Gateway->>IdentityService: Validate JWT
    Gateway->>TenantService: Resolve tenant plan + context
    Gateway->>Microservices: Forward with X-Tenant-Id
Hold "Alt" / "Option" to enable pan & zoom

Tip

Multi-tenant resolution is modular and supports dynamic edition-level routing for different SLAs.

🛒 E-Commerce Checkout Flow

Scenario: Handle real-time checkout with downstream services (order, inventory, billing).

Responsibilities: - Route /api/checkout to a dedicated façade endpoint - Aggregate inventory, payment, and order status in one response - Enforce rate limits on anonymous traffic - Fallback to secondary payment gateway

graph TD
    Client --> Gateway
    Gateway --> OrderService
    Gateway --> InventoryService
    Gateway --> BillingService
Hold "Alt" / "Option" to enable pan & zoom

Policy: 

routes:
  - path: /api/checkout
    rateLimit: 10rps
    fallback: /api/fallback/payment

🏥 Healthcare System (B2B and PHI Access)

Scenario: Support secure access to patient data with compliance and auditing.

Responsibilities: - Validate access tokens issued by Azure AD B2C or OpenIddict - Inject user identity, role, and session metadata - Enforce scope-based access (appointments:read, records:write) - Full traceability for audit logs (PHI-level)

if (!user.HasScope("appointments:read"))
{
    return Unauthorized();
}

Headers Injected: 

X-User-Id: 123
X-Tenant-Id: vetclinic001
X-Scopes: appointments:read appointments:book

🤖 AI Assistant Orchestration (Agents, Webhooks, Tracing)

Scenario: Use gateway to route AI prompts to orchestrators, kernel-based agents, or inference services.

Responsibilities: - Route /ai/* requests to semantic kernel or inference engine - Add headers for user language, persona, subscription tier - Enable OpenTelemetry for tracing each step (e.g., embedding, planner, summarizer)

graph TD
    UI --> Gateway
    Gateway --> AIKernel
    Gateway --> EmbeddingService
    Gateway --> MemoryStore
    Gateway --> LoggingService
Hold "Alt" / "Option" to enable pan & zoom

Use Case Routes: - /ai/respond - /ai/infer/medical - /ai/tools/image

⚙️ DevOps API Gateway for CI/CD Pipelines

Scenario: Internal gateway for interacting with secure build, deploy, and audit endpoints.

Responsibilities: - Authenticate internal agents with machine-scoped JWTs - Rate limit long-polling agents (webhooks, release triggers) - Route to deployment microservices (Terraform, Helm, Pulumi)

Example Pattern: 

graph TD
    BuildAgent --> Gateway
    Gateway --> DeployService
    Gateway --> AuditLog
    Gateway --> ArtifactStore
Hold "Alt" / "Option" to enable pan & zoom

Info

These internal gateways can run in isolated namespaces and enforce service-to-service policies using mTLS and RBAC.

🔄 Backend for Frontend (BFF) Variant

Scenario: Mobile app needs single endpoint to pull user dashboard.

Responsibilities: - Compose responses from multiple services (e.g., UserService, NotificationService, TasksService) - Format response to mobile-specific schema - Cache recent responses for burst load

{
  "user": {...},
  "notifications": [...],
  "tasks": [...]
}

Optimized for: - Low-latency mobile environments - Edge deployments (API Gateway + CDN) - App-specific API shaping

🧠 Summary of Common Gateway Patterns

Pattern Description
Multi-Tenant Gateway Auth + tenant resolution + scoped rate limits
API Composition Aggregate multiple downstream calls into one response
Façade Endpoint Abstract and secure a service (e.g., checkout, billing)
AI Pipeline Proxying Route and trace GPT/embedding flows
mTLS Internal Gateway Service-to-service calls inside protected mesh
BFF / Aggregator Gateway Deliver frontend/mobile optimized APIs
Low-Traffic Public Gateway Edge proxy with static caching, fallback + quota control

🧩 Best Practices for API Gateway in ConnectSoft

Area Best Practice
Authentication Validate JWTs early at the gateway; propagate user/tenant metadata downstream
Authorization Enforce role/scope at the gateway level, not just in services
Tenant Context Resolve tenant from claims, headers, or route; inject into every request
Observability Always enrich logs, traces, and metrics with correlation IDs and tenant IDs
Routing & Composition Prefer simple forwarding; compose responses only when necessary (BFF pattern)
Rate Limiting & Quotas Rate limit at gateway, separate by authentication type (free vs. paid)
Resilience Implement retries + circuit breakers; fail gracefully with fallback responses
Configuration Management Use environment-specific settings, injected secrets, and structured config
Extensibility Add middleware for custom policies, diagnostics, and dynamic routing
Security Compliance Sanitize all incoming headers; terminate TLS at the gateway boundary
Deployment Use Helm, Pulumi, and CI/CD pipelines for repeatable, observable deployments
Scaling Auto-scale API Gateway independently from backend services

🧠 Conclusion

The ConnectSoft API Gateway is not a generic reverse proxy — it is a purpose-built, production-grade solution tailored for:

  • 🏢 Multi-tenant SaaS Platforms
  • 🛒 E-commerce systems
  • 🏥 Healthcare and regulated environments
  • 🤖 AI orchestration and inference pipelines
  • ⚙️ Internal DevOps automation

By centralizing routing, authentication, tenant resolution, rate limiting, and observability —
the gateway decouples client access from service architecture, improves security and performance, and empowers scalability across any cloud or hybrid infrastructure.

Every ConnectSoft microservice, SaaS edition, and platform integration relies on the consistent, modular, and observable behavior provided by the Gateway.

💡 ConnectSoft Principle:
"The Gateway is not just the system's front door — it is its first layer of trust, control, and insight."

With built-in support for OpenTelemetry, structured logging, distributed tracing, dynamic resilience policies, and custom extension points, the ConnectSoft API Gateway ensures that every system remains secure, scalable, auditable, and evolution-ready.

📚 References and Related Documents

📖 Core ConnectSoft Documentation

📘 Concepts and Technologies