Distributed Systems in 3 Minutes: CDNs, APIs, TCP & Idempotency Explained

Key Takeaways

Every Google search, Netflix stream, or UPI payment touches a distributed system. But what does that actually mean? In the next 3 minutes, let's break down the fundamentals using one simple road map. What is a distributed system? A distributed system is a group of computers that work together to appear like a single coherent system to the user. Some machines can fail while others continue running, which makes design and reliability much harder than on a single server. CDN impact. First, content delivery networks or CDNs. Without a CDN, every user talks directly to your origin server, often far away, causing latency and bottlenecks. With a CDN, copies of your static content are cached on edge servers closer to users, reducing latency and improving reliability when a single region struggles. API evolution. Next, how systems talk to each other has evolved over decades. 1960s sub routines and libraries mostly within one machine. 1980s remote procedure calls RPCs to call functions on remote machines. 1990s SOAP web services with XML and strict contracts. 2000s and beyond REST APIs using HTTP and JSON simpler and web native now the default for most services. TCP basics. To connect machines reliably, distributed systems lean on TCP. The client sends a SYN packet. The server replies with SY and ACK and the client responds with ACK. This three-way handshake establishes a reliable connection before data flows. This helps detect lost packets and ensures order delivery which higher level protocols like HTTP depend on. It impotency keys. In real systems, networks fail and clients retry requests. If a payment or order creation is retried, you do not want to create duplicates. An ITM potency key is a unique token attached to a request so the server can recognize repeated submissions and only process them once, returning the same result for subsequent retries. Non-retriable failures backslash. Finally, not every error should be retried. Client errors like HTTP 400 mean the request is malformed and will fail again. Authentication errors like 401 or 43 mean credentials are invalid. 404 indicates the resource does not exist. 422 validation errors and programming bugs require fixing logic, not hitting retry. Mastering these basics, CDNs, APIs, TCP, it impotency and error handling is the foundation for designing reliable distributed systems.