this is the cached addresses

Step A: Registration & Heartbeat When a "Server" instance (the service providing the data) boots up, it sends a REST call to the Service Registry to register itself. It then sends a "heartbeat" (a tiny ping) every few seconds. If the heartbeat stops, the Registry removes that server from the list.

Step B: Discovery (The Pull) When the "Client" (the service needing the data) starts up, it reaches out to the Service Registry and says: "Give me the current list of all healthy instances for 'Payment-Service'." It saves this list locally.

Step C: Selection (The Logic) When your code actually executes a call (e.g., restTemplate.getForObject("http://payment-service/pay")), the load balancer library intercepts the request. It looks at its local cache and sees three IPs:

10.0.0.1

10.0.0.2

10.0.0.3

It applies an algorithm—usually Round Robin (cycling through them) or Random Selection—to pick one.

Step D: The Direct Call The client swaps the service name (payment-service) for the real IP address (10.0.0.2) and sends the request directly to that server. No middleman is involved in the actual data transfer.

1. The Fundamental Split Kernel Space: The privileged "inner sanctum" of the OS. It has direct access to hardware (Network Card, Memory, CPU). It is stable but hard to update. User Space: Where applications (Chrome, Nginx) live. It is restricted and cannot touch hardware directly; it must ask the Kernel to send data.
2. HTTP/1.1 & HTTP/2 (The TCP Era) Location of Logic: Kernel Space. Division of Labor: App (User Space): Creates the HTTP request (Layer 7). OS (Kernel Space): Handles Layer 4 (TCP). It does the "Packaging & Sequencing," retransmission of lost packets, and flow control. The Bottleneck: To change how packets are handled, you have to update the whole Operating System. Every request requires a "Context Switch" (crossing the border from App to Kernel), which is slow.
3. HTTP/3 (The QUIC/UDP Era) Location of Logic: User Space. Division of Labor: App (User Space): Handles both Layer 7 (HTTP) and the "Smart" parts of Layer 4 (QUIC). The app does its own packaging, sequencing, and encryption. OS (Kernel Space): Acts as a "dumb pipe" using UDP. It just tosses the app’s pre-packaged boxes out to the network card without looking inside. The Innovation: The transport logic is now a "library" inside the app, not a feature of the OS.

Devices in different homes (or networks) can absolutely have the same private IP address without any conflict. Why this works

Private IPs are only meaningful inside a single local network.

So:

Your home Wi-Fi → its own “mini world” Your neighbor’s Wi-Fi → another separate “mini world”

👉 These worlds don’t directly see each other