# Load Balancing Options — Azure

Source: https://www.skillbyai.com/en/azure/n-lb

> Choose between Load Balancer, Application Gateway, Front Door and Traffic Manager.

## Regional or global, layer 4 or layer 7

Azure has four load-balancing services, chosen along two axes. **Azure Load Balancer** is **regional, layer 4** (TCP/UDP): very fast, no understanding of HTTP, used in front of VMs and scale sets. **Application Gateway** is **regional, layer 7**: TLS termination, path-based routing (`/api` versus `/images`), cookie affinity and an optional **Web Application Firewall (WAF)**. **Azure Front Door** is **global, layer 7**: it runs on Microsoft's edge network, routes users to the closest healthy backend across regions, caches content like a CDN and includes WAF. **Traffic Manager** is **global and DNS-based**: it answers DNS queries with the endpoint chosen by priority, weighting, performance or geography, so it works for any protocol but fails over only as quickly as DNS caches expire.

## Decision table

A quick way to pick a service in design reviews.

```text
need                                           service
---------------------------------------------  -------------------------
TCP/UDP spread over VMs in one region          Azure Load Balancer
HTTP routing + WAF inside one region / VNet    Application Gateway
global HTTP entry, edge caching, WAF, failover Azure Front Door
global failover for non-HTTP endpoints via DNS Traffic Manager

common combo: Front Door (global) -> App Gateway or App Service (regional) in 2 regions
```

## Health probes decide everything

Every load balancer routes only to backends its health probe considers healthy. Point probes at a lightweight `/health` endpoint that checks critical dependencies, not at `/`, which may return 200 while the database is down.

**Quiz:** You need a single global HTTPS entry point with WAF and edge caching that fails over between two regions. Which service fits best?

- [x] Azure Front Door
- [ ] Azure Load Balancer
- [ ] Application Gateway
- [ ] Network security group

*Answer:* Azure Front Door. Front Door is the global layer-7 service with WAF, caching and multi-region routing.