API Governance for Engineering Organizations

How to organize and manage microservice APIs at scale.

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API Registry

The Registry is the system of record for all API metadata, serving as the central source of truth for API specifications, versions, subscriptions, and governance policies. It provides both human-facing interfaces and machine-readable APIs for the entire platform.

2.1 Core Registry Components

High-Level Architecture

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flowchart TB
    subgraph External["External Systems"]
        Producer[API Producer Teams]
        Consumer[API Consumers]
        DevPortal[Developer Portal]
        CICD[CI/CD Pipeline]
    end
    
    subgraph Registry["API Registry Core"]
        RegistryAPI[Registry API Layer]
        Catalog[API Catalog]
        Subscription[Subscription Mgmt]
        Schema[Schema Registry]
        Policy[Policy Engine]
        Discovery[Service Discovery]
    end
    
    subgraph Platform["Platform Services"]
        Gateway[API Gateway]
        Auditor[API Auditor]
    end
    
    Producer --> RegistryAPI
    Consumer --> RegistryAPI
    DevPortal <--> RegistryAPI
    CICD --> RegistryAPI
    
    RegistryAPI --> Catalog
    RegistryAPI --> Subscription
    RegistryAPI --> Schema
    RegistryAPI --> Policy
    RegistryAPI --> Discovery
    
    Gateway <--> RegistryAPI
    Auditor <--> RegistryAPI
    Discovery --> Gateway
    
    style Registry fill:#e8f4f8,stroke:#2c5aa0,stroke-width:3px
    style External fill:#f0f0f0,stroke:#666,stroke-width:2px
    style Platform fill:#fff4e6,stroke:#ff9900,stroke-width:2px

Registry Internal Components

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flowchart LR
    subgraph Core["Core Services"]
        Catalog[API Catalog & Metadata]
        Subscription[Subscription Management]
        Schema[Schema Registry & Compatibility]
        Policy[Policy & Governance]
        Discovery[Service Discovery & Routing]
    end
    
    subgraph Support["Support Services"]
        API[Registry API]
        Notify[Notifications & Events]
    end
    
    API --> Catalog
    API --> Subscription
    API --> Schema
    API --> Policy
    API --> Discovery
    
    Catalog -.-> Notify
    Subscription -.-> Notify
    Policy -.-> Notify
    
    style Core fill:#e8f4f8,stroke:#2c5aa0,stroke-width:2px
    style Support fill:#f0f9ff,stroke:#0066cc,stroke-width:2px

Data Storage Layer

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flowchart TB
    subgraph Services["Registry Services"]
        Catalog[API Catalog]
        Subscription[Subscriptions]
        Schema[Schema Registry]
        Policy[Policy Engine]
        Discovery[Service Discovery]
    end
    
    subgraph Storage["Data Storage"]
        DB[(PostgreSQL Primary DB)]
        ES[(Elasticsearch Search Index)]
        Redis[(Redis Cache)]
        Git[Git Repo Version Control]
    end
    
    subgraph Integration["External Integration"]
        Kafka[Kafka Event Bus]
        Vault[HashiCorp Vault Secrets]
        K8s[Kubernetes Service Discovery]
    end
    
    Catalog --> DB
    Catalog --> ES
    Catalog --> Git
    Catalog --> Kafka
    
    Subscription --> DB
    Subscription --> Redis
    Subscription --> Vault
    Subscription --> Kafka
    
    Schema --> DB
    Policy --> DB
    Policy --> Kafka
    
    Discovery --> DB
    Discovery --> Redis
    Discovery <--> K8s
    
    style Services fill:#e8f4f8,stroke:#2c5aa0,stroke-width:2px
    style Storage fill:#fff9e6,stroke:#cc9900,stroke-width:2px
    style Integration fill:#f0e6ff,stroke:#9900cc,stroke-width:2px

API Catalog & Metadata Management

Purpose: Stores and manages comprehensive metadata about all APIs in the organization.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Subscription Management System

Purpose: Tracks which consumers have access to which APIs and manages the subscription lifecycle.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Schema Registry & Compatibility Checker

Purpose: Enforces backward compatibility and manages schema evolution across API versions.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Policy & Governance Engine

Purpose: Defines, stores, and enforces governance policies across the API lifecycle.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Service Discovery & Routing Configuration

Purpose: Maintains the mapping between API specifications and backend service instances.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

2.2 Registry Management & Supporting Services

Registry API (Public & Internal)

Purpose: Provides programmatic access to Registry data for platform components and external integrations.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Notification & Event Service

Purpose: Sends notifications about API changes and lifecycle events to stakeholders.

Key Responsibilities:

Technical Implementation:

Inputs:

Outputs:

Registry Admin UI & Management Console

Purpose: Web-based interface for Registry administrators to manage the platform.

Key Responsibilities:

Technical Implementation:

2.3 Registry Data Model & Storage

Core Entities:

Protocol-Specific Storage: | Protocol | Specification Format | Validation Tool | Schema Registry | |———-|———————|—————–|—————–| | REST | OpenAPI 3.x (YAML/JSON) | Spectral | Not required | | GraphQL | SDL schema | graphql-inspector | GraphQL schema registry | | AsyncAPI | AsyncAPI 2.x (YAML/JSON) | asyncapi-parser | Schema Registry (Avro/JSON Schema) | | gRPC | Protocol Buffers (.proto) | protoc compiler | Buf Schema Registry |

Database Design:

Data Integrity:

Performance Optimization:

2.4 Registry Deployment & Operations

High Availability:

Scaling:

Observability:

Security:

Next: API Auditor

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