SDKs1 min read

Go SDK

Zero-dependency Go SDK with http.Handler middleware for any Go web framework.

Docs  SDKs  Overview

When to Use SDKs#

SDKs are the code-first integration path. Use them when:

No gateway present

Internal microservices, background jobs, or CLI tools that bypass the API gateway

Granular feature gating

Application-level entitlement checks that need access to business context (user role, session state)

Custom metering logic

Billing for computed metrics (tokens processed, MB stored, minutes elapsed) not visible at the gateway

Hybrid enforcement

Gateway handles basic rate limiting; SDK handles fine-grained entitlement and margin checks inside the app

Node.js#

terminal

npm install @aforo/metering

Express Middleware (5 lines)

app.js

const { AforoClient } = require('@aforo/metering');

const aforo = new AforoClient({
  apiKey: process.env.AFORO_API_KEY,
  tenantId: process.env.AFORO_TENANT_ID,
});

// Wrap any Express route — metering is automatic
app.use('/api', aforo.expressMiddleware({
  metricId: 'api_calls',
  tenantIdHeader: 'x-tenant-id',
}));

Manual Metering

usage.js

// Meter a custom event (e.g., AI tokens consumed)
await aforo.meter({
  metricId: 'ai_tokens',
  quantity: completionTokens + promptTokens,
  properties: { model: 'gpt-4o', endpoint: '/v1/chat' },
});

// Check entitlements before executing expensive logic
const access = await aforo.canAccess('advanced_search');
if (!access.allowed) {
  return res.status(403).json({ error: 'Plan upgrade required' });
}
// access.remaining_quota → 8420

Python#

terminal

pip install aforo-metering

FastAPI Decorator

main.py

from aforo_metering import AforoClient, aforo_middleware

aforo = AforoClient(
    api_key=os.environ["AFORO_API_KEY"],
    tenant_id=os.environ["AFORO_TENANT_ID"],
)

# Decorator — automatically meters every request
@app.get("/api/search")
@aforo.wrap_handler(metric_id="api_calls")
async def search(query: str):
    return {"results": await do_search(query)}

Django Middleware

settings.py

MIDDLEWARE = [
    ...
    'aforo_metering.DjangoMiddleware',
]

AFORO_CONFIG = {
    'api_key': os.environ['AFORO_API_KEY'],
    'tenant_id_header': 'X-Tenant-Id',
    'default_metric': 'api_calls',
}

Go#

terminal

go get github.com/aforo/metering-go

http.Handler Wrapper

main.go

package main

import (
    "net/http"
    aforo "github.com/aforo/metering-go"
)

func main() {
    client := aforo.NewClient(aforo.Config{
        APIKey:   os.Getenv("AFORO_API_KEY"),
        TenantID: os.Getenv("AFORO_TENANT_ID"),
    })

    // Wrap any http.Handler — zero dependencies
    mux := http.NewServeMux()
    mux.Handle("/api/", client.Middleware("api_calls", yourHandler))
    http.ListenAndServe(":8080", mux)
}

Java / Spring Boot#

pom.xml

<dependency>
  <groupId>com.aforo</groupId>
  <artifactId>metering-spring-boot-starter</artifactId>
  <version>1.0.0</version>
</dependency>

Auto-Configuration

application.yml

aforo:
  api-key: ${AFORO_API_KEY}
  tenant-id-header: X-Tenant-Id
  default-metric: api_calls
  batch-size: 100
  flush-interval-ms: 5000

SearchController.java

@RestController
public class SearchController {

    @Autowired
    private AforoClient aforo;

    @GetMapping("/api/search")
    public ResponseEntity<?> search(@RequestHeader("X-Tenant-Id") String tenantId) {
        // Entitlement check
        EntitlementResponse access = aforo.canAccess(tenantId, "advanced_search");
        if (!access.isAllowed()) {
            return ResponseEntity.status(403).body("Plan upgrade required");
        }

        // Business logic...
        SearchResult result = doSearch();

        // Meter custom usage
        aforo.meter(tenantId, "search_queries", 1, Map.of("type", "advanced"));
        return ResponseEntity.ok(result);
    }
}

SDK vs. Gateway: When to Use Which#

CriteriaGateway PluginSDK

Code changesZeroMinimal (middleware/decorator)

Metering granularityRequest-levelCustom (tokens, bytes, compute time)

Entitlement latency<5ms (edge cache)<10ms (Redis or in-memory)

Best forAPI products with gatewayInternal services, CLI tools, background jobs

Margin GuardFull L1-L3L1 (alert) + L2 (in-app throttle)

 PRO TIP

Most enterprises use both. The gateway plugin handles 90% of API traffic automatically. SDKs handle the remaining 10% — internal services, background processing, and custom metering for AI workloads where token counts matter more than request counts.