WHAT HAPPENS WHEN YOU TYPE https://www.google.com AND PRESS ENTER
This is a concise, end-to-end walkthrough that covers DNS, TCP/IP, firewalls, HTTPS/TLS, load balancers, web servers, application servers, and databases.
1) DNS — turning a name into an address
- The browser/OS/DNS resolver looks up www.google.com.
- If not cached, the resolver queries root > .com TLD > google.com authoritative DNS.
- It gets an A (IPv4) or AAAA (IPv6) record, or a CNAME that points to a hostname with A/AAAA.
- TTL controls how long results are cached.
2) TCP/IP — connecting to the right port
- The client opens a TCP connection to the server IP on port 443 (HTTPS).
- TCP does the the three-way handshake (SYN, SYN-ACK, ACK).
3) Firewall — only the right traffic gets in
- Network firewalls/security groups permit only allowed traffic, e.g., TCP/443 to the edge.
- Non-matching packets are dropped.
4) HTTPS / TLS — encrypting and authenticating
- The browser and server perform a TLS handshake over port 443.
- The server sends an X.509 certificate for www.google.com (CA-signed).
- They agree on a cipher suite and derive shared keys.
- HTTP data is now encrypted and integrity-protected.
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5) Load balancer — spreading requests
- An edge load balancer distributes traffic to healthy backends (round-robin, least-connections, etc.).
- It can terminate TLS and optionally re-encrypt to backends.
- It enforces health checks and traffic policies.
6) Web server — HTTP optimization and reverse proxying
- Serves static assets efficiently; reverse-proxies dynamic requests to the app server.
- Can add compression, caching, connection pooling to upstreams.
7) Application server — business logic
- Reads cookies/headers, checks auth, runs business logic, calls internal services.
- Renders HTML or returns JSON.
8) Database — persistent state
- The app queries databases (SQL/NoSQL), caches, indexes.
- Common: primary for writes, replicas for reads.
- App builds the response and returns it via web server and LB to the browser.
9) Quick recap in one line...
🌐 DNS → 🔌 TCP 443 → 🛡️ Firewall → 🔒 TLS → ⚖️ Load Balancer → 🕸️ Web Server → ⚙️ App Server → 🗄️ Database → 👤 Browser
10) Diagram