Ingress Controller OR API Gateway, Which one you Choose!

If you're managing external traffic for microservices, you've probably come across both Ingress Controllers and API Gateways. But knowing which one to use, and when, is where many teams get stuck.

The simple truth? They overlap in some functions, but they serve very different architectural roles.

Let's break it all down.

What Is an Ingress Controller?

An Ingress Controller is a Kubernetes-native component that acts as the front door for HTTP and HTTPS traffic entering your cluster. It interprets routing rules defined in Kubernetes Ingress resources and forwards requests to the appropriate service and then to backend pods.

What does an Ingress Controller actually do?

It operates like a Layer 7 reverse proxy (typically NGINX, Traefik, or HAProxy), offering:

• Path-based and host-based routing
• TLS/SSL termination at the edge
• Basic rate limiting
• Load balancing across multiple pod replicas
• Rewrite and redirect rules
• Integration with cert-manager for auto-renewing HTTPS

How is an Ingress Controller used?

You define an Ingress resource in YAML, which maps a URL or path to a backend service. The Ingress Controller watches the Kubernetes API for these resources, updates its configuration in real time, and ensures external requests are directed properly.

Why use an Ingress Controller?

Ingress Controllers can help you:

Reduce cloud cost by minimizing the number of LoadBalancers

Centralize security, TLS, and routing logic

Keep routing Kubernetes-native without needing third-party tooling

Perfect for HTTP/S microservices that don't need full API lifecycle management

To learn more about Ingress Controllers, also read: Ingress Controller Architecture For Kubernetes | Setup, Security & Scalability

What Is an API Gateway?

An API Gateway is a centralized API management component that sits at the edge of your system (inside or outside Kubernetes) and handles much more than just routing.

It's designed to manage external consumer-facing APIs, often offering enterprise-grade features like:

Authentication (OAuth2, JWT, API keys)

Rate limiting, quotas, and throttling

Request/response transformation (e.g., XML to JSON)

API versioning and deprecation policies

Built-in developer portals and documentation

Usage analytics, billing integration, and monitoring

gRPC and WebSocket support alongside HTTP/S

What does an API Gateway actually do?

It acts as an intelligent broker between clients and your microservices. Instead of clients calling services directly, they call the API Gateway. The Gateway authenticates, inspects, modifies (if needed), and routes the request to the proper backend.

How is an API Gateway used?

You deploy the gateway (like Kong, Tyk, Apigee, or AWS API Gateway), configure routing and security policies, and optionally integrate it with CI/CD pipelines to manage API changes programmatically.

Why use an API Gateway?

Use an API Gateway if:

• You're exposing APIs to third parties or mobile apps
• You need fine-grained control over how APIs are consumed
• You want to decouple authentication, versioning, and access control from your core services
• Ideal for API-first or multi-cloud architectures

Ingress Controller Architecture vs API Gateway Architecture

Though both tools handle inbound traffic, they're architecturally and functionally different in critical ways.

Placement in the System

Ingress Controllers are Kubernetes-native and run as pods inside your cluster. They're deployed and managed using the same tools as your apps.

API Gateways typically sit at the edge, outside or just before the cluster, often integrated into external DNS or API management platforms.

Supported Protocols

Ingress Controllers are primarily designed for Layer 7 HTTP/HTTPS traffic only.

API Gateways can handle a wider range of protocols like HTTP/HTTPS, WebSocket, gRPC, MQTT, and even GraphQL, depending on the tool.

Purpose and Capabilities

Ingress Controllers handle simple routing (path-based, host-based), TLS termination, and basic load balancing.

API Gateways are for managing the full lifecycle of APIs: authentication, rate limiting, versioning, request/response transformation, and more.

Configuration & Management

Ingress Controllers are configured via Kubernetes Ingress resources (YAML). They react to cluster changes dynamically.

API Gateways are configured using their own dashboards, CRDs, plugins, or APIs, and often require separate management layers.

Security & Governance

Ingress Controllers offer TLS termination and basic IP filtering.

API Gateways offer robust security controls: OAuth2, JWT validation, mTLS, API keys, WAF integration, and audit logging.

Observability & Monitoring

Ingress Controllers expose standard metrics via Prometheus and logs via stdout/stderr.

API Gateways offer advanced observability: per-user analytics, request tracing, SLA dashboards, and integration with SIEM tools.

Deployment Scenarios

Ingress Controllers are ideal for internal service routing in microservices architectures hosted on Kubernetes.

API Gateways are ideal for external-facing APIs, multi-tenant API products, or hybrid deployments spanning Kubernetes, VMs, and server-less environments.

Now that we've broken it down, here's a quick visual comparison:

When to Use an Ingress Controller or API Gateway?

There's no one-size-fits-all answer to this. Choose based on what kind of traffic you manage and what kind of control you need.

Use an Ingress Controller when:

You're routing HTTP/S traffic between services inside a Kubernetes cluster

You want something lightweight, declarative, and native to Kubernetes

Your services are internal or frontend-facing without public developer consumption

Use an API Gateway when:

You're exposing APIs to external users or applications

You need advanced authentication, quotas, or transformation

You want to monetize APIs or offer self-service to external developers

Many teams use both: an Ingress Controller for basic cluster routing, and an API Gateway layered behind it for managing exposed APIs.

Kubernetes Ingress Alternatives and API Gateway Alternatives

Before you settle, it's worth exploring the evolving ecosystem.

Ingress Controller alternatives:

Istio or Linkerd Gateway: Service mesh gateways that offer more observability and security

Envoy Proxy: Great if you want programmable control with powerful filters

Custom reverse proxies: NGINX/HAProxy with manual config

API Gateway alternatives:

Service Mesh with API gateway add-ons: Combine service-level mesh with API security

Build your own using open-source proxies with Lua, WASM, or Go extensions

Sidecar architectures: For ultra-granular API control across services

Your choice should reflect your architecture maturity, protocol diversity, and security needs.

But there's a catch. Both API Gateways and standard Ingress Controllers are designed primarily for HTTP-based traffic. But what if your traffic isn't HTTP at all?

Where Does Ecosmob's SIP Ingress Controller Fit In?

So far, everything we've discussed applies to HTTP/S traffic. What if you're handling something else entirely, like SIP, VoIP, or WebRTC?

These aren't typical API workloads. They use session-based protocols, dynamic ports, and require persistent, low-latency connections. And this is where neither Ingress Controllers nor API Gateways are enough.

So we built the perfect solution: an SIP Ingress Controller!

It's purpose-built for Kubernetes-native real-time traffic and solves problems that standard tools can't:

Dynamic Pod Discovery for SIP workloads (via K8s APIs)

SIP Header-Based Routing (e.g., DID, codecs, protocol)

Autoscaling with Zero Downtime Call Failover

TLS & SRTP Encryption for signaling and media

Compatible with UDP, TCP, and TLS transport protocols

If you're running a UCaaS platform, VoIP app, or SIP trunking infrastructure, this is the ingress solution built for your reality.

There's a reason so many teams mix up Ingress Controllers and API Gateways - they both sit at the entry point.

But one is for simple, declarative routing inside Kubernetes. The other is for full-featured API management across systems.

And if your traffic is real-time, session-based, and SIP-heavy?

You need something altogether different.

Ecosmob's SIP Ingress Controller is how telecom teams bring Kubernetes to life for real-time voice, media, and messaging apps at scale.

Ready to route smarter? Talk to us today!

Source Link: https://www.ecosmob.com/api-gateway-vs-ingress-controller/