Config Service Architecture

                    Config Service (Port 8888)
                           |
    +----------+-----------+-----------+-----------+
    |          |           |           |           |
 REST API   WebSocket   Kafka      Health     Actuator
 (12 ctrl)  (streaming) (events)   (/health)  (/prometheus)
    |          |           |           |           |
    +----------+-----------+-----------+-----------+
                           |
              +------------+------------+
              |            |            |
         Service Layer   Cache Layer  Audit Layer
         (13 services)   (Redis)     (change tracking)
              |            |            |
              +------------+------------+
                           |
              +------------+------------+
              |            |            |
         JPA Repos     Redis Repos   Kafka Producer
         (14 repos)    (cache)       (change events)
              |            |            |
              +------------+------------+
                           |
                      PostgreSQL

// ConfigService.getConfigWithHierarchy()
// 1. Check tenant+environment specific config
// 2. Fall back to tenant-level config
// 3. Fall back to environment-level config
// 4. Fall back to global config
public Optional<ConfigEntry> getConfigWithHierarchy(
        UUID tenantId, String configKey, String environment) {
    // Tenant + environment specific
    Optional<ConfigEntry> tenantEnv = repository.findByTenantIdAndConfigKeyAndEnvironment(
            tenantId, configKey, environment);
    if (tenantEnv.isPresent()) return tenantEnv;
 
    // Tenant level
    Optional<ConfigEntry> tenant = repository.findByTenantIdAndConfigKey(tenantId, configKey);
    if (tenant.isPresent()) return tenant;
 
    // Global
    return repository.findByTenantIdIsNullAndConfigKey(configKey);
}

@Entity
@Table(name = "config_entries")
public class ConfigEntry {
    @Id
    private UUID id;
    private UUID tenantId;          // null for global configs
    private String configKey;        // e.g., "query.timeout"
    private String configValue;      // the value
    private String category;         // grouping category
    private String description;
    private String environment;      // dev, staging, production
    private String valueType;        // STRING, INTEGER, BOOLEAN, JSON
    private boolean encrypted;       // whether value is encrypted
    private Integer version;         // auto-incrementing version
    private UUID createdBy;
    private Instant createdAt;
    private Instant updatedAt;
}

@Entity
@Table(name = "feature_flags")
public class FeatureFlag {
    @Id
    private UUID id;
    private UUID tenantId;
    private String flagKey;
    private String displayName;
    private String description;
    private String flagType;         // BOOLEAN, STRING, NUMBER, JSON
    private boolean enabled;
    private String defaultValue;
    private Integer rolloutPercentage;
    private List<UUID> allowedUsers;
    private List<Map<String, Object>> rules;  // targeting rules (JSON)
    private Set<String> tags;
    private Instant createdAt;
    private Instant updatedAt;
}

{
  "eventType": "CONFIG_UPDATED",
  "configId": "550e8400-e29b-41d4-a716-446655440000",
  "tenantId": "660e8400-e29b-41d4-a716-446655440000",
  "configKey": "query.timeout",
  "oldValue": "60s",
  "newValue": "120s",
  "changedBy": "admin@acme.com",
  "environment": "production",
  "timestamp": "2026-02-12T10:00:00Z",
  "correlationId": "req-abc-123"
}

server:
  port: 8888
 
spring:
  datasource:
    url: jdbc:postgresql://${DB_HOST}:5432/matih_config
    username: ${DB_USERNAME}
    password: ${DB_PASSWORD}
  redis:
    host: ${REDIS_HOST}
    port: 6379
  kafka:
    bootstrap-servers: ${KAFKA_BOOTSTRAP_SERVERS}
 
config-service:
  encryption:
    algorithm: AES/GCM/NoPadding
    key-length: 256
  cache:
    ttl: 300s
    max-size: 10000
  scheduling:
    poll-interval: 30s