System Design Made Simple
Algomi Research · 2026-09-15 · System Design
An original learning series for technical blogs and interview preparation.
Edition: 1.0 · Updated: 15 September 2026
Start with a familiar problem
Imagine a school library. Students want to find books, reserve a copy, and get a message when it is ready. One teacher can manage a small library with a notebook. A library used by many schools needs a better plan.
Software grows in much the same way. System design explains how to choose its parts, connect them, and keep them useful when traffic grows or something breaks.
The series uses short explanations first. More precise details follow under trade-offs, examples, and interview questions. Technical words are kept because interviewers use them, but each is explained in everyday language.
The five guides
| Read | Guide | What you will learn |
|---|---|---|
| 1 | Foundations and data | Requirements, estimates, scaling, databases, caching, replication, consistency, CAP, PACELC, hashing |
| 2 | Networking and APIs | IP, DNS, HTTP, TCP/UDP, CDNs, load balancers, proxies, API styles, live updates |
| 3 | Architecture, messaging, and patterns | Layers, monoliths, microservices, queues, streams, outbox, sagas, CQRS, event sourcing, object design patterns |
| 4 | Reliability, security, and operations | Availability, failover, circuit breakers, rate limits, recovery, identity, encryption, deployment, monitoring |
| 5 | Interview workbook and case studies | Interview structure, worked designs, scenario practice, research reading, revision plan |
There are 50 numbered interview questions across the guides. These are original practice questions, not a claim about questions asked by particular employers.
How to use the diagrams
Diagrams are Mermaid diagrams rendered directly on each guide's page. The diagrams describe teaching designs. They do not claim to reproduce a company's private architecture.
Technical corrections carried into the guides
| Easy-to-memorize but misleading claim | More useful understanding |
|---|---|
| CAP means pick any two of three | During a network partition, linearizable consistency and availability for every request cannot both be guaranteed |
| Strong consistency updates all replicas at the same instant | It is an observable guarantee; coordination can provide it without every replica being current |
| A FIFO queue makes every business action happen once | Ordering and duplicate handling are separate; external effects still need protection |
| Streaming platforms cannot track consumers | Log systems can store consumer progress and offer configurable delivery guarantees |
| TCP guarantees the business request succeeded | TCP provides an ordered byte stream; the application can still fail or time out |
| Public IP means every network has one shared address | NAT often shares an address, but public addressing is not defined by that arrangement |
| Replication is a backup | Replication can copy accidental deletion; recoverable history is a separate requirement |
| Microservices automatically isolate failures | Synchronous dependencies and shared infrastructure can still spread failures |
| OAuth and OIDC are interchangeable | OAuth delegates access; OIDC adds identity information for login |
| A singleton is unique across a cluster | A normal singleton controls an object within a runtime scope |
The relevant guides link to primary references for the key corrections. Technology-specific behavior should always be checked against the version and configuration actually being used.