🛠️ API Design and Management¶

APIs are the backbone of modern platforms, powering communication between services, frontend clients, third-party integrators, and infrastructure. In a distributed system — whether microservices, serverless, or event-driven — clean, secure, and observable APIs are critical to scalability and maintainability.

Info

At ConnectSoft, APIs are treated as first-class assets — carefully designed, documented, secured, and evolved across every platform, SaaS solution, microservice, and AI system.
Our approach ensures that APIs are not just technical endpoints, but reliable contracts, enforceable policies, and scalable products that enable integration, innovation, and growth at every layer.

At ConnectSoft, API design is not an afterthought — it's a first-class design activity embedded into our platform templates, domain modeling process, and deployment pipelines.

🔍 Introduction¶

A well-designed API is more than just a contract between systems. It reflects domain intent, enforces security boundaries, and delivers a developer experience that scales across teams and integrations.

The ConnectSoft API strategy integrates with:

🧱 Domain-Driven Design (DDD)
🧪 Test-First Use Cases
🚀 Automated CI/CD and versioning
🔐 Built-in authentication, tenant resolution, and scope policies
📊 Observability via OpenTelemetry and structured logs
🧠 Event-based and request-based communication models

APIs are the primary surface through which value is delivered to platforms, partners, and customers.

🧭 API Design Objectives¶

Objective	ConnectSoft Perspective
Clarity	APIs reflect domain models and are self-explanatory in naming and behavior
Security	Authentication and authorization are enforced at the edge and service layers
Extensibility	APIs support optional fields, versioning, and evolution without breaking clients
Observability	Every request is traceable, measurable, and audit-logged
Governance	Contract-first, versioned, testable, and policy-driven
Developer UX	APIs are discoverable, documented, testable, and mockable

🔧 API Types in ConnectSoft Systems¶

ConnectSoft solutions use a mix of API interaction styles depending on use case, latency requirements, and client needs:

API Type	Description	Typical Use
REST	Stateless HTTP API with resource-based modeling	CRUD operations, external integrations
GraphQL	Declarative API with client-driven query shape	Mobile apps, multi-platform frontends
gRPC	High-performance protocol using HTTP/2 and Protobuf	Internal service-to-service comms
Webhooks	Server-to-client event notifications	3^rd-party integrations, async updates
Event APIs	Publish-subscribe or queue-based models	Decoupled workflows, cross-service events

🌉 Example: Multi-Protocol Architecture¶

graph TD
    WebApp -->|REST| Gateway
    MobileApp -->|GraphQL| Gateway
    Gateway -->|gRPC| InventoryService
    Gateway -->|gRPC| OrderService
    InventoryService -->|Events| Kafka
    OrderService -->|Events| Kafka
    PartnerSystem -->|Webhooks| Gateway

Hold "Alt" / "Option" to enable pan & zoom

Tip

Each ConnectSoft platform includes templates to generate REST, GraphQL, and gRPC endpoints out-of-the-box, with authentication and observability pre-wired.

📐 API Design Principles¶

ConnectSoft APIs follow industry-leading design principles reinforced by code templates and architectural linting:

✅ Consistency¶

Use plural nouns for collections: /products, /orders
Use nouns + subresources: /users/{id}/settings
Standardize on lowercase with hyphens for paths: /tenant-invitations

✅ Clarity¶

Avoid ambiguous verbs: use POST /orders/submit only if it represents a domain action
Always return structured responses (no raw strings or booleans)

✅ HTTP Semantics¶

GET = read
POST = create
PUT = replace
PATCH = partial update
DELETE = remove

✅ Semantic Errors¶

Use error envelopes with machine-readable codes and human-readable messages

{
  "error": {
    "code": "order_already_shipped",
    "message": "Cannot cancel order that has already shipped."
  }
}

✅ Pagination and Filtering¶

Use standard query params:
GET /products?limit=25&offset=0
GET /users?email=alice@example.com

🧱 Contract-First Design¶

At ConnectSoft, API design is done before implementation, using structured contracts and testable specs.

OpenAPI Example:

openapi: 3.0.0
info:
  title: Subscription API
  version: 1.0.0
paths:
  /subscriptions:
    post:
      summary: Create a subscription
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/NewSubscription'
      responses:
        '201':
          description: Created

Workflow:

Define OpenAPI contract (*.yaml)
Commit to /Contracts/ folder in Git
Generate DTOs and controllers via template
Validate with contract tests (Pact or SpecFlow)
Wire into CI/CD pipeline

🧠 API Design Fundamentals¶

API design is not only about exposing functionality — it's about expressing domain meaning, preserving contract stability, and guiding how consumers interact with the system.

In ConnectSoft, every API must be predictable, evolvable, and observable. To ensure this, we apply several core principles across all design layers.

📚 Resource Modeling¶

APIs should model real-world concepts using nouns and their relationships. Avoid designing around internal DB tables or low-level entities.

✅ Good Example¶

GET /orders
GET /orders/{orderId}
POST /orders

❌ Anti-Example¶

POST /createOrder
GET /getOrderDetails?id=123

Tip

Use RESTful URIs and standard verbs. Behavior-specific commands can still exist, but they should represent domain actions (/orders/{id}/cancel).

📦 Resource Relationships¶

Model nested resources only when there is clear ownership or containment.

Use Case	Recommended URI
User’s settings	`/users/{id}/settings`
Order’s items	`/orders/{id}/items`
Shared resource	`/invoices/{id}`

🧪 Input Validation and Schema Standards¶

Validate incoming payloads at the API boundary, close to the controller level, using schemas (OpenAPI), attribute-based validation, or FluentValidation.

Example: FluentValidation Rule

RuleFor(x => x.Email)
    .NotEmpty()
    .EmailAddress();
RuleFor(x => x.Quantity)
    .GreaterThan(0);

ConnectSoft APIs use auto-generated Swagger from annotated DTOs and validation middleware to ensure unified behavior.

🧱 Response Structure¶

Every response, success or error, should be wrapped in a predictable envelope. This helps frontend and third-party clients parse, handle, and log responses systematically.

Success Envelope

{
  "data": {
    "orderId": "abc123",
    "status": "processing"
  },
  "meta": {
    "timestamp": "2024-04-25T10:00:00Z",
    "correlationId": "xyz-789"
  }
}

Error Envelope

{
  "error": {
    "code": "invalid_email_format",
    "message": "The email address is not valid.",
    "field": "email"
  }
}

Tip

Error responses should always include a machine-readable code, an optional field, and a human-friendly message.

🚨 Standardized Error Handling with Problem Details and Exception Mapping¶

At ConnectSoft, every API error response must comply with the Problem Details format defined in RFC7807.
Errors are translated automatically from domain exceptions into structured, traceable responses — improving consistency, developer experience, and observability.

Info

Exception mapping to Problem Details is applied across the entire platform.
Custom domain exceptions, validation errors, and infrastructure issues are surfaced with rich metadata, without leaking internal details.

📄 Problem Details Standard at ConnectSoft¶

Example API error response:

{
  "type": "https://docs.connectsoft.io/errors/order_already_shipped",
  "title": "Order Cannot Be Cancelled",
  "status": 409,
  "detail": "The order has already been shipped and cannot be cancelled.",
  "instance": "/orders/12345",
  "correlationId": "c123-xyz",
  "tenantId": "tenant-456",
  "errorCode": "ORDER_ALREADY_SHIPPED"
}

Field	Description
`type`	Link to documentation about the specific error
`title`	Human-readable summary of the error
`status`	HTTP status code
`detail`	Additional contextual details
`instance`	Request URI that caused the problem
`correlationId`	ConnectSoft traceability (same as request logs)
`tenantId`	ConnectSoft tenant context
`errorCode`	Internal domain-specific classification

🛠️ Exception to ProblemDetails Mapping¶

Instead of manually handling exceptions everywhere, ConnectSoft uses global exception mapping middleware.

Each domain exception is mapped to an appropriate Problem Details object automatically.

Example: Custom Domain Exceptions

public class OrderAlreadyShippedException : DomainException
{
    public OrderAlreadyShippedException(Guid orderId)
        : base($"Order {orderId} has already been shipped.") { }
}

Global Exception Handler (ProblemDetails Middleware Extension):

app.UseExceptionHandler(config =>
{
    config.Run(async context =>
    {
        var exception = context.Features.Get<IExceptionHandlerFeature>()?.Error;
        var problem = MapExceptionToProblemDetails(exception, context);

        context.Response.StatusCode = problem.Status ?? (int)HttpStatusCode.InternalServerError;
        context.Response.ContentType = "application/problem+json";

        await context.Response.WriteAsJsonAsync(problem);
    });
});

static ProblemDetails MapExceptionToProblemDetails(Exception exception, HttpContext context)
{
    return exception switch
    {
        OrderAlreadyShippedException ex => new ProblemDetails
        {
            Type = "https://docs.connectsoft.io/errors/order_already_shipped",
            Title = "Order Cannot Be Cancelled",
            Detail = ex.Message,
            Status = StatusCodes.Status409Conflict,
            Instance = context.Request.Path,
            Extensions =
            {
                ["correlationId"] = context.TraceIdentifier,
                ["tenantId"] = context.User.FindFirst("tenant_id")?.Value,
                ["errorCode"] = "ORDER_ALREADY_SHIPPED"
            }
        },
        ValidationException ex => new ValidationProblemDetails(ex.Errors)
        {
            Type = "https://docs.connectsoft.io/errors/validation_failed",
            Title = "Validation Failed",
            Status = StatusCodes.Status400BadRequest,
            Instance = context.Request.Path,
            Extensions =
            {
                ["correlationId"] = context.TraceIdentifier,
                ["tenantId"] = context.User.FindFirst("tenant_id")?.Value,
                ["errorCode"] = "VALIDATION_FAILED"
            }
        },
        _ => new ProblemDetails
        {
            Type = "https://docs.connectsoft.io/errors/internal_server_error",
            Title = "Internal Server Error",
            Detail = "An unexpected error occurred.",
            Status = StatusCodes.Status500InternalServerError,
            Instance = context.Request.Path,
            Extensions =
            {
                ["correlationId"] = context.TraceIdentifier
            }
        }
    };
}

📋 Best Practices for Problem Details at ConnectSoft¶

Practice	Description
Map each domain exception	Define a unique ProblemDetails `type` URL and `errorCode`
Include correlationId and tenantId	For full observability and traceability
Localize user-facing titles/messages	Especially for SaaS and multi-region platforms
Avoid leaking internal stack traces	Always sanitize error responses
Return ValidationProblemDetails for model errors	Include per-field errors dictionary

📣 Example: Validation Error Response¶

{
  "type": "https://docs.connectsoft.io/errors/validation_failed",
  "title": "Validation Failed",
  "status": 400,
  "detail": "Request validation failed. See errors for details.",
  "instance": "/subscriptions",
  "errors": {
    "email": ["The Email field is invalid."],
    "quantity": ["Quantity must be greater than 0."]
  },
  "correlationId": "def-456",
  "tenantId": "tenant-789",
  "errorCode": "VALIDATION_FAILED"
}

📈 Why Problem Details Exception Mapping Matters¶

🔥 Unified developer experience: All APIs behave consistently on errors
🔎 Observability: Errors can be traced instantly across systems via correlation IDs
🧩 Contract safety: Clients can parse errors predictably by errorCode
🔐 Security: Internal failures are hidden from clients, only meaningful context is surfaced

🧠 Diagram: Exception to ProblemDetails Mapping Flow¶

sequenceDiagram
    Client->>API Gateway: API Request
    API Gateway->>Service: Forward Request
    Service->>Service: Throw DomainException (e.g., OrderAlreadyShippedException)
    Service-->>Exception Middleware: Capture Exception
    Exception Middleware-->>ProblemDetails Mapper: Map Exception to ProblemDetails Response
    ProblemDetails Mapper-->>API Gateway: Return ProblemDetails JSON
    API Gateway-->>Client: 4xx or 5xx Structured ProblemDetails Response

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🔢 Versioning Strategy¶

API versions are mandatory at ConnectSoft — no versionless endpoints are allowed.

✅ Preferred: URI Versioning¶

GET /v1/users
GET /v2/orders

Easy to test, cache, and evolve
Supported by all API gateways and proxies

Alternative: Header Versioning¶

GET /users
X-API-Version: 2

Cleaner URI
Works well with client libraries or SDKs

Warning

Never mix versioning strategies within the same API surface. Choose one and apply consistently.

📦 Field Evolution and Compatibility¶

APIs must evolve without breaking clients:

Pattern	Rule
Add new fields	Safe (clients ignore unknown fields)
Remove existing fields	Breaking change (requires new version)
Change field meaning	Breaking (requires version change)
Add enum value	Breaking for some clients (must document and version if critical)

Best Practice:
Add new optional fields, document clearly, and provide fallback behavior when absent.

🧱 OpenAPI Style Conventions¶

All ConnectSoft APIs must define their contracts using OpenAPI 3.x. Style guidelines include:

Element	Convention
`components`	Organized by schema/use case
`operationId`	Must match UseCase handler
`tags`	Reflect bounded context name
`enum`	Lowercase + underscore
`nullable`	Explicit (no hidden nulls)

Example: Schema Block

components:
  schemas:
    OrderStatus:
      type: string
      enum: [pending, processing, shipped, delivered, cancelled]

🔁 Pagination and Filtering¶

Paginated endpoints must support:

limit (default: 25, max: 100)
offset or cursor
totalCount in response metadata

GET /v1/orders?limit=50&offset=100

Paginated Response Format

{
  "data": [...],
  "meta": {
    "limit": 50,
    "offset": 100,
    "totalCount": 1240
  }
}

Filtering should follow consistent query syntax:

GET /users?email=admin@example.com&isActive=true

✅ Best Practices Summary¶

Category	Guideline
URIs	Use nouns, plural form, avoid verbs
Verbs	Use standard HTTP methods
Naming	Consistent casing and terminology across API
Validation	Use schema validation with clear error messages
Responses	Always structured in envelopes with metadata
Versioning	Prefer URI versioning, be explicit and predictable
Pagination	Implement limit/offset with consistent metadata
Contracts	Use OpenAPI and commit `.yaml` files to source with lint rules

🧩 API Architecture Patterns and Integration Styles¶

Different application layers and client types require different API integration styles. At ConnectSoft, we use a mix of REST, GraphQL, gRPC, and event-driven interfaces — with each carefully selected for the scenario.

🧠 Choosing the Right Integration Style¶

Pattern	When to Use	Notes
REST	Simple CRUD, public APIs, predictable clients	Cacheable, well-known
GraphQL	UI-driven apps, mobile apps, bandwidth-constrained clients	Query shaping, flexible
gRPC	Internal service-to-service comms, low-latency, typed interactions	High performance
Webhooks	Third-party notifications, async responses	Must support retries
Events	Distributed workflows, eventual consistency, decoupled services	Pub/Sub or queues

🕸️ REST at ConnectSoft¶

REST is used as the default API layer for:

Public client APIs
Admin portals
Tenant management
Settings and configuration

Each REST API follows standard ConnectSoft rules:
- GET /resource
- POST /resource
- PATCH /resource/{id}
- DELETE /resource/{id}

GET /v1/tenants/123/features
Authorization: Bearer {token}

Response Example

{
  "data": [
    { "feature": "ExportCSV", "enabled": true }
  ]
}

🧠 GraphQL APIs¶

GraphQL is used in systems where flexible querying and UI adaptation is critical, e.g.:

📱 Mobile and tablet clients
📦 Multilingual SaaS interfaces
📊 Embedded dashboards and analytics

Query Example

query {
  user(id: "123") {
    name
    settings {
      timezone
      preferredLanguage
    }
  }
}

ConnectSoft Enhancements:

Schema registered at /graphql endpoint
Introspection disabled in production
Role/Scope guards per field and resolver
Observability and tracing via Apollo plugins

⚙️ gRPC Services¶

gRPC is used for internal service-to-service communication:

🧾 Billing
🧠 AI Inference engines
🔄 Real-time status propagation
📊 Analytics workers

Proto Example:

service InvoiceService {
  rpc GetInvoice (InvoiceRequest) returns (InvoiceResponse);
}

Tip

gRPC endpoints are documented in .proto files and compiled into internal SDKs via Grpc.Tools.

📣 Webhooks and Callbacks¶

Used for:

User provisioning in external systems
Payment notifications
Partner system integrations

Example Event Flow

sequenceDiagram
    ServiceA->>PartnerSystem: POST /webhook/user_created
    PartnerSystem-->>ServiceA: 200 OK

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Security Practices:

Signed payloads with HMAC or shared secrets
Retries with exponential backoff
Idempotency tokens

🧠 Event-Driven APIs (Pub/Sub)¶

Used in ConnectSoft for:

Inventory events
Appointment scheduling notifications
Email/SMS events
Audit trails and change data capture (CDC)

Event Format (JSON)

{
  "event": "inventory_updated",
  "data": {
    "productId": "abc123",
    "quantity": 42
  },
  "timestamp": "2024-04-25T12:00:00Z"
}

Published to:

Azure Event Grid
Kafka
RabbitMQ topics

🎭 Backend-for-Frontend (BFF)¶

In mobile-first platforms, ConnectSoft uses BFF gateways that expose:

Aggregated user dashboard views
Tenant-scoped search results
Profile + preference + permissions in one call

Example Flow

sequenceDiagram
    MobileApp->>BFF: GET /dashboard
    BFF->>UserService: GET /user/123
    BFF->>PermissionsService: GET /user/123/roles
    BFF->>FeatureService: GET /user/123/features
    BFF-->>MobileApp: JSON Aggregated Response

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⚙️ Orchestration vs. Choreography¶

🎛️ Orchestration¶

A central orchestrator coordinates all interactions.

Use Case: Subscription provisioning flow.

graph TD
    Orchestrator --> UserService
    Orchestrator --> SubscriptionService
    Orchestrator --> EmailService

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🎼 Choreography¶

Each service listens and reacts to domain events.

Use Case: Order shipping flow.

graph TD
    OrderPlaced --> Inventory
    OrderPlaced --> Billing
    OrderPlaced --> Notification

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Comparison	Orchestration	Choreography
Control Flow	Centralized	Decentralized
Coupling	Tighter	Looser
Observability	Easier to trace	Requires event tracing
Fault Tolerance	Single point of failure risk	More resilient

🧰 Integration Guidance¶

Pattern	Tools / Tech Stack
REST	ASP.NET Core, Swagger/OpenAPI
GraphQL	HotChocolate, StrawberryShake, Apollo
gRPC	Grpc.AspNetCore, Protobufs
Webhooks	ASP.NET Controllers, Polly, Redis Queue
Pub/Sub Events	MassTransit, Azure Service Bus, Kafka

🔁 API Versioning and Lifecycle Evolution¶

APIs are long-lived assets. Over time, they evolve to support new features, security requirements, or performance optimizations. At ConnectSoft, API evolution is planned, documented, and communicated carefully to avoid breaking consumer applications.

🧱 Versioning Strategies¶

URI Versioning (Recommended)¶

GET /v1/users
GET /v2/orders

Advantages:
Explicit
Easy to test and cache
Supported by gateways, proxies, and OpenAPI

Header-Based Versioning (Optional)¶

GET /users
X-API-Version: 2

Advantages:
- Clean URLs
Disadvantages:
- Harder to debug
- Requires strict documentation and SDK compliance

Query Parameter Versioning (Discouraged)¶

GET /users?version=2

Often ambiguous and less cache-friendly

Tip

All APIs must start versioned at /v1/. Never expose unversioned public endpoints.

🛑 Breaking Changes: What Counts?¶

Change Type	Breaking?	Requires New Version?
Add optional field	❌	No
Rename or remove field	✅	Yes
Change field meaning	✅	Yes
Modify enum values	⚠️	Yes (if clients validate enums)
Change status codes	✅	Yes

🧠 Deprecation Policies¶

ConnectSoft enforces a deprecation lifecycle that is visible, communicated, and controlled.

Process¶

Announce deprecation (documentation, changelogs)
Add Sunset header to responses
Monitor usage via observability layer
Fully disable after transition window

Example Sunset Header¶

Sunset: Tue, 30 Sep 2025 00:00:00 GMT
Deprecation: true
Link: </v2/users>; rel="successor-version"

🔂 Backward Compatibility Rules¶

To evolve safely, APIs must:

Handle unknown fields gracefully
Avoid renaming or removing fields mid-version
Provide default values for newly added fields
Introduce optional fields as non-breaking changes
Expose x-connectsoft-version in headers for diagnostics

Compatible Schema Change

{
- "name": "Alice"
+ "name": "Alice",
+ "preferredLanguage": "en"
}

🧪 Test for Version Compatibility¶

Use automated tests in CI pipelines:

Regression suite using contract-based test tools (e.g. Pact, Postman, SpecFlow)
Backward compatibility tests per version (/v1, /v2)
Traffic replay tools to simulate production payloads

🔐 Semantic Versioning (SemVer) for APIs¶

Apply SemVer concepts to API design:

v1.0.0: Stable initial release
v1.1.0: Add non-breaking functionality
v2.0.0: Introduce breaking changes

ConnectSoft publishes API changelogs with semantically versioned diffs:

[Added] New /v1/invoices/bulk endpoint
[Deprecated] /v1/payments/{id}/refund moved to /v2/payments/refund
[Fixed] Bug in pagination metadata rounding logic

📣 Communicating Changes¶

Channel	Purpose
OpenAPI `description`	Inline changes and guidance
Changelog.md	Track additions, fixes, removals
Email / Portal Notices	Notify integrators of sunset schedules
SDK Release Notes	Alert consuming apps of interface changes

📦 ConnectSoft Versioning Best Practices¶

Practice	Description
✅ Start at v1	Always version public APIs from the start
✅ Never break consumers silently	Changes must go through formal versioning
✅ Use `Sunset` headers	Signal upcoming deprecations in all responses
✅ Maintain parallel versions	Run `/v1` and `/v2` concurrently during transition
✅ Avoid versionless webhooks	Even callback APIs should indicate version context

🧰 Tools for Version Management¶

Tool / Process	Usage
Swagger/OpenAPI	Document each version separately
Postman	Organize environments by API version
Azure API Management	Route versions and enforce sunset via policies
Git Contracts Folder	Store each OpenAPI spec per version in source control
Changelog Generators	Automatically diff versions for client consumption

🔁 Evolution Workflow¶

graph TD
    Plan[Plan Change] --> Define[Define Contract]
    Define --> Version[Version Resource or Path]
    Version --> Deprecate[Mark Old Version with Sunset]
    Deprecate --> Monitor[Monitor Usage]
    Monitor --> Sunset[Disable After Sunset Date]

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🔐 API Security and Threat Protection¶

Security is non-negotiable in modern API-driven systems. At ConnectSoft, every exposed API — public or internal — is protected by defense-in-depth mechanisms, including strict authentication, scope-based authorization, tenant validation, and traffic filtering.

🧾 Authentication Strategies¶

Method	Description	Usage in ConnectSoft
OAuth2	Standard token-based auth flow	Browser apps, mobile, third-party integrations
JWT	Compact, signed tokens with claims	Default bearer tokens in all APIs
API Keys	Simple keys passed in header	Internal automation, limited-scope scripts
mTLS	Mutual TLS, certificate-based auth	Service-to-service in restricted environments

Example: OAuth2 Access Token (JWT)

{
  "sub": "user-123",
  "tenant_id": "tenant-xyz",
  "scope": "appointments:read",
  "exp": 1714687277
}

JWT Validation Middleware:

services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.Authority = "https://auth.connectsoft.io";
        options.Audience = "connectsoft-api";
    });

🧑‍🤝‍🧑 Tenant-Aware Authorization¶

All ConnectSoft APIs are multi-tenant by default. Authorization is enforced via:

Scopes and roles encoded in JWTs
Tenant context extracted from claims or headers
API gateway middleware that injects X-Tenant-Id headers

Authorization Flow:

sequenceDiagram
    Client->>API Gateway: Authenticated Request (JWT)
    API Gateway->>AuthService: Validate JWT, resolve scopes
    API Gateway->>Service: Forward request + X-Tenant-Id header
    Service->>AuthorizationHandler: Check role/scope for tenant

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🎯 Scope-Based Access Control¶

ConnectSoft uses a scope-based permission model for fine-grained access control:

Scope	Description
`orders:read`	Read-only access to orders
`orders:write`	Create or update orders
`admin:manage`	Full administrative control
`billing:approve`	Approve billing workflows

Scope Enforcement Snippet:

if (!user.HasScope("orders:write"))
{
    return Forbid();
}

Scopes are validated at both the gateway and the application level.

🧱 Threat Mitigation Patterns¶

🛡️ Input Validation¶

Enforce schema-level validation for all inbound requests
Reject unknown or unexpected fields
Use library-based validation (FluentValidation, Data Annotations)

[Required]
[EmailAddress]
public string Email { get; set; }

🚧 SQL Injection Defense¶

Always use parameterized queries
Avoid raw SQL construction via string interpolation

await connection.QueryAsync("SELECT * FROM users WHERE email = @Email", new { Email = input });

🔐 Encryption in Transit and at Rest¶

Enforce HTTPS (TLS 1.2+)
Use Azure Key Vault or managed cloud secrets
AES-256 encryption for sensitive fields

📈 Rate Limiting and Throttling¶

ConnectSoft gateways enforce tiered quota enforcement:

User Type	Requests/Minute	Notes
Free Tier	60	Soft limited with burst
Premium Tier	1000	Higher quota, fair queue
Internal Bots	Unlimited (scoped)	Identified by service token

{
  "rate_limit": {
    "limit": 1000,
    "remaining": 237,
    "reset": "2024-04-25T15:00:00Z"
  }
}

Gateway Policy Example (Kong YAML):

plugins:
  - name: rate-limiting
    config:
      minute: 100
      limit_by: consumer

🚨 DDoS and Abuse Prevention¶

Technique	Purpose
Geo-blocking	Block regions not in target market
IP Filtering	Deny suspicious or internal IPs
Bot Detection	Challenge requests with high error rate
Cloud Shields	Use Azure DDoS Protection, AWS Shield

🔍 Auditing and Log Correlation¶

All security-critical events are logged with:

User ID
Tenant ID
Token ID or fingerprint
Correlation ID
Action and resource path

Log Entry Example (JSON):

{
  "timestamp": "2024-04-25T14:00:00Z",
  "action": "update_user",
  "userId": "u-123",
  "tenantId": "t-456",
  "correlationId": "abc-789",
  "status": "success"
}

✅ Security Best Practices Summary¶

Area	Practice
🔐 Authentication	Use OAuth2 with signed JWTs
🧑‍🤝‍🧑 Multi-Tenancy	Validate tenant and inject into all downstream service calls
🔎 Scopes	Apply least-privilege access model
🧪 Input Validation	Use schema, size, format, and enum validation
🔐 Encryption	TLS for all transport, AES-256 for sensitive fields
🚦 Rate Limiting	Enforce quotas by user tier and token scope
🧾 Auditing	Log every action with traceability metadata
🧱 API Gateway Rules	Strip dangerous headers, limit payload size, enforce allowed methods

📊 API Observability and Monitoring¶

In ConnectSoft systems, APIs are built to be observable from day one.
Visibility into API behavior enables performance optimization, security auditing, incident detection, and system evolution.

Observability spans across:

📋 Structured Logging
📈 Metrics Collection
🕸️ Distributed Tracing
📣 Alerting and Incident Response

📋 Structured Logging¶

Every ConnectSoft API generates structured logs in a machine-readable JSON format, enriched with:

Timestamps
Correlation IDs
Tenant IDs
User IDs (when applicable)
Route and method
Status codes
Execution duration

Log Example:

{
  "timestamp": "2025-04-25T10:15:30Z",
  "correlationId": "c123-abc",
  "tenantId": "tenant-789",
  "userId": "user-456",
  "method": "GET",
  "path": "/v1/orders/123",
  "statusCode": 200,
  "latencyMs": 120
}

Best Practices:

Practice	Notes
Use correlation IDs	Trace entire request flow across services
Mask sensitive fields	Never log passwords, secrets, tokens
Capture structured JSON	Avoid free-text logs; use log templates

📈 Metrics Collection¶

Metrics help detect issues before they become incidents.

Metric	Purpose	Example Tool
Request Rate (`http_requests_total`)	Throughput monitoring	Prometheus
Latency (`http_request_duration_seconds`)	Detect performance regressions	Grafana
Error Rate (`http_errors_total`)	Detect spikes in failures	Prometheus
Saturation Metrics	Monitor CPU/memory, DB pool saturation	Azure Monitor

Example Prometheus Query:

rate(http_request_duration_seconds_sum[5m]) / rate(http_request_duration_seconds_count[5m])

Service-Level Objectives (SLOs):

95% of requests under 400ms latency
Error rate <1% over a rolling 1-hour window

🕸️ Distributed Tracing (OpenTelemetry)¶

Tracing provides full request visibility across microservices, message queues, databases, and external APIs.

Trace Data Captures:

Span duration
Service-to-service hops
Error annotations
Tenant-specific metadata

Trace Example Flow:

sequenceDiagram
    Client->>API Gateway: API Request (correlationId: abc123)
    API Gateway->>OrderService: Forwarded Request
    OrderService->>InventoryService: Check Stock
    InventoryService-->>OrderService: Stock Confirmed
    OrderService-->>API Gateway: Order Placed
    API Gateway-->>Client: 201 Created

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Toolchain:

OpenTelemetry SDK in all APIs
Trace export to Jaeger or Azure Application Insights
Context propagation (traceparent, baggage headers)

🛎️ Alerting and Incident Response¶

Automated alerts based on metric thresholds ensure proactive incident management.

Alert Type	Trigger Condition	Action
High Error Rate	>1% error responses over 5 minutes	Trigger PagerDuty escalation
Latency Spike	>500ms p95 for a critical route	Slack alert + ticket creation
API Saturation	CPU >85% or DB Pool Exhaustion	Auto-scale instance, inform ops
Deprecation Breach	Traffic to deprecated API version after sunset date	Block and alert compliance team

Example Alert Configuration (Prometheus Rule):

groups:
- name: APIAlerts
  rules:
  - alert: HighRequestLatency
    expr: histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) > 0.5
    for: 5m
    labels:
      severity: warning
    annotations:
      summary: "High latency detected on API"

🧰 Observability Tools Stack¶

Area	Recommended Tool
Logging	Serilog → ElasticSearch → Kibana
Metrics	Prometheus → Grafana
Tracing	OpenTelemetry → Jaeger or Azure Monitor
Incident Management	PagerDuty, Opsgenie, Azure Alerts

📐 ConnectSoft Observability Architecture¶

flowchart TD
    API_Gateway -->|Structured Logs| LogAggregator
    API_Gateway -->|Traces| TraceCollector
    API_Gateway -->|Metrics| PrometheusServer
    LogAggregator --> ElasticSearch
    PrometheusServer --> Grafana
    TraceCollector --> Jaeger

Hold "Alt" / "Option" to enable pan & zoom

📋 Logs centralized and searchable (ElasticSearch, Kibana)
📈 Metrics visualized (Grafana)
🕵️‍♂️ Traces linked to correlation IDs across services (Jaeger, OpenTelemetry)

✅ Observability Best Practices¶

Practice	Notes
Correlate logs, metrics, and traces	Use correlation IDs across the stack
Alert on symptoms, not just errors	Watch for latency increases, not just 500s
Dashboard everything	Visualize KPIs, error trends, and request distribution
Proactive incident playbooks	Define how to react to common types of alerts

🏆 Best Practices Recap¶

ConnectSoft enforces a disciplined and structured approach to API design, management, and evolution.
Here’s a final recap of essential best practices applied across all projects:

📐 API Design¶

Area	Practice
Resource Modeling	Use nouns, not verbs; reflect domain entities clearly
Consistency	Uniform naming, response structures, and HTTP semantics
Validation	Enforce input validation at the boundary
Error Handling	Use standard, structured error envelopes
Pagination & Filtering	Standardize query parameters, metadata structure
Versioning	Always expose versioned URIs from v1 onward
OpenAPI	Maintain contract-first OpenAPI specs per version

🔐 Security¶

Area	Practice
Authentication	OAuth2 flows with signed JWTs
Authorization	Scope-based and tenant-aware access controls
Input Protection	Validate schemas, sizes, types, and ranges
Transport Security	TLS 1.2+ encryption enforced on all connections
Rate Limiting	Protect APIs with tiered quotas and burst management
Auditing	Log all sensitive activities with correlation IDs

📊 Observability¶

Area	Practice
Structured Logging	JSON logs with rich metadata (tenantId, userId, latency)
Metrics	Request rates, error rates, latency, resource saturation
Distributed Tracing	Correlate all service hops with OpenTelemetry
Alerting	Proactive incident detection via metrics and thresholds

🔁 Evolution¶

Area	Practice
Semantic Versioning	Major.Minor.Patch semantics for API releases
Deprecation	Sunset headers and announced migration paths
Contract Testing	Automated verification of backward compatibility
Changelog Discipline	Detailed, structured changelogs for consumers

🧠 Final Conclusion¶

APIs are not simply endpoints — they are contracts, policies, and products.

At ConnectSoft, our approach to API design and management ensures:

Interoperability across distributed systems
Security by enforcing defense-in-depth patterns
Scalability to support millions of interactions daily
Observability for real-time monitoring, auditability, and evolution
Developer Experience that accelerates integration and platform adoption

Good API design is a long-term investment: every good decision made at the design phase saves 10× effort in scaling, securing, and maintaining complex systems later.

"An API is your handshake to the world. Design it with clarity, secure it with trust, and manage it with wisdom."