Software Architecture

The Roots

The word "Architect" has its roots in Ancient Greek ἀρχιτέκτων (arkhitéktōn), meaning chief builder or master craftsman:

ἀρχι — chief, leader, primary
τέκτων — builder, carpenter, craftsman

The oldest known treatise on architecture is De architectura by the Roman architect Marcus Vitruvius Pollio, written around 25 BC. Vitruvius defined three principles that every well-designed structure must balance:

Vitruvius dedicated separate books to temples, public buildings, and private houses — recognizing that each type of building demands its own design approach. Software is no different.

Architecture as an Art

In some cases, architecture is seen as an art. Some buildings are designed primarily for their aesthetic impact or as a display of wealth and tastefulness.

Architecture as a Craft

In some cases, architecture is seen as the craft of creating a plan. The plan serves two purposes: (1) it is easier to review and change a plan than to change a building under construction, and (2) builders can work independently from the plan without needing constant instructions. Depending on constraints, the goal may be a standard plan that fits most customers, or an individual plan for unique requirements.

Little or common constraints and requirements

There are cases where an architect has few constraints or little variance in the constraints and requirements (e.g. when the cost of land is low or the needs of the customers are all about the same). In this case, it is relatively simple to build on the experience from past projects to improve future projects.

Individual constraints and requirements

There are cases with unique constraints and requirements. There it is important to have knowledge about a broad range of possible solutions and the advantages and disadvantages.

The goals of the plan

The first goal of the plan is to fit the constraints and requirements of the customer.

The second goal of the plan is to fit the constraints and requirements of the builders.

Architecture for different types of buildings

There are different types of buildings. The architect as the master craftsman shall have lots of experience. With the diversity of the building types, it is unlikely that an architect is a master craftsman for multiple building types, usually you need a whole lifetime to master all the aspects of just one building type.

Examples of different types of buildings

Buildings come in many different types, each designed for a specific purpose.

Alpine Hut

Aqueduct

Factory

Holiday Resort

Railway Station

Single Family Home (Tibet)

Single Family Home (Mongolia)

Single Family Home (USA)

Skyscraper

Traffic Bridge

Examples of different types of building material

Buildings can be constructed from a wide range of materials.

Property	Steel	Stone (Natural)	Reinforced Concrete	Woodwork (Engineered Wood)	Wood (Solid Timber)	Calcium Silicate	Brick (Clay)	Aerated Concrete (AAC)	Mudbrick (Adobe)
Density	Very high (7850 kg/m³)	Very high (2600 kg/m³)	High (2400 kg/m³)	Low–medium (600 kg/m³)	Low (500 kg/m³)	High (2000 kg/m³)	Medium (1800 kg/m³)	Very low (500 kg/m³)	Medium (1500 kg/m³)
Compressive Strength	Very high (250 MPa)	Very high (100 MPa)	High (30–50 MPa)	Medium–high (35 MPa)	Medium (30 MPa parallel)	High (25 MPa)	Medium (20 MPa)	Low (4 MPa)	Low (2 MPa)
Thermal Insulation	Very poor	Poor	Poor	Good–very good	Good	Poor	Moderate	Very good	Good
Sound Insulation	Poor	Very good	Good	Moderate	Moderate	Very good	Moderate–Good	Poor–moderate	Good
Moisture Behavior	Corrosion-prone without protection	Very low absorption	Low absorption (if sealed)	Improved stability vs. solid wood	Sensitive (swelling/decay)	Moderate absorption	Regulates moisture well	High absorption	Very sensitive to water
Fire Resistance	Poor (loses strength ~500°C)	Excellent	Good–excellent	Moderate (predictable charring)	Poor–moderate (chars)	Excellent	Excellent	Excellent	Good
Weight	Very heavy	Very heavy	Very heavy	Light–medium	Light	Heavy	Heavy	Very light	Medium
Workability	Difficult (specialized tools)	Difficult	Moderate (formwork required)	Easy–moderate	Easy	Moderate	Moderate	Very easy	Easy
Typical Use	Structural frames, bridges, high-rises	Structural & cladding	Foundations, slabs, high-rises	Beams, panels (CLT, glulam)	Structural frames, houses	Load-bearing, soundproof walls	Masonry walls	Lightweight walls, insulation	Traditional walls (dry climates)
Durability	Very high (if protected)	Very high	Very high	High	Moderate	Very high	High	Moderate	Low–moderate
Cost (relative)	High	High	Medium–high	Medium–high	Medium	Low–medium	Medium	Medium	Low

Examples of the diversity of single family wood houses

Even with the same type and material, buildings can look very different.

Normal single family wood house

Large single family wood house

Different types of software

Just like buildings, software comes in many different types, each designed for a specific purpose with its own set of characteristics, technologies, and trade-offs.

Attribute	Desktop	Telecom	CAD	Media & Entertainment	Mobile	Embedded	Trading	E-Commerce
Estimated Global LOC	~350B	~300B	~200B	~200B	~175B	~125B	~100B	~275B
Common Programming Languages	C#, C++, Java, Python	C, C++, Java, Erlang	C++, Python, C#	C++, C#, Python, JavaScript	Kotlin, Swift, Dart, JavaScript	C, C++, Rust, Assembly	Java, C++, Python, Rust	Java, JavaScript, Python, PHP, Go
Common Frameworks / Platforms	.NET, Qt, Electron, JavaFX	5G stacks, OpenRAN, Kubernetes, OSS/BSS	OpenCASCADE, Qt, .NET	Unity, Unreal Engine, FFmpeg	Android SDK, iOS SDK, Flutter, React Native	FreeRTOS, Zephyr, Embedded Linux	Spring, FIX engines, Kafka	Spring Boot, Shopify, Magento, React, Node.js
Prominent Architectural Styles	Microservices, layered architecture, MVC/MVVM, plugin architecture, event-driven UI	Distributed systems, microservices, event-driven architecture, actor model (Erlang), service-oriented architecture (SOA)	Layered + domain-driven design, plugin architecture, command pattern, model-view separation	Component-based architecture, entity-component-system (ECS), event-driven, client-server, streaming pipelines	MVVM/MVC, clean architecture, offline-first, client-server, reactive programming	Bare-metal / layered, real-time scheduling, interrupt-driven design, state machines	Event-driven architecture, microservices, CQRS, actor model, pipeline/stream processing	Microservices, layered architecture, MVC, event-driven, domain-driven design
Key Architectural Characteristics	Rich UI/UX, OS integration, responsiveness, local storage, modularity	High availability, scalability, real-time processing, fault tolerance, distributed systems	High precision, geometry modeling, performance, large datasets, extensibility	High performance (graphics/audio), real-time rendering, scalability, cross-platform, UX	Battery efficiency, responsive UI, offline capability, network handling, device integration	Deterministic behavior, low memory, real-time constraints, hardware interaction, reliability	Low latency, high throughput, fault tolerance, consistency, real-time data	Scalability, high availability, security, fast page load, payment integration
Not Important Characteristics	Hard real-time, ultra-low memory, extreme fault tolerance	Rich UI, rapid prototyping, small codebase, low complexity	Ultra-low latency networking, small footprint, mobile UX, rapid UI iteration	Strict determinism, ultra-low memory, simple logic, minimal dependencies	Batch processing, extreme precision computing, massive parallelism	Fancy UI, cloud scalability, rapid iteration, dynamic memory	Rich UI design, small binary size, offline-first, device UX	Ultra-low latency, real-time constraints, embedded hardware, small binary size
Example Applications	Microsoft Word, Visual Studio, Notepad++, Photoshop	5G core, IMS, VoIP platforms, SMS gateways	AutoCAD, SolidWorks, Fusion 360, CATIA	Unreal Engine games, Netflix, Adobe Premiere, Spotify	WhatsApp, Instagram, Google Maps, TikTok	Car ECUs, IoT sensors, routers, smart appliances	MetaTrader, Bloomberg Terminal, Robinhood, E*TRADE	Amazon, Shopify, eBay, Zalando

Common architectural styles

Just as buildings are constructed from different materials — each with its own strengths, weaknesses, and best-fit scenarios — software systems are built using different architectural styles. The choice of style shapes the system's structure, behavior, and trade-offs.

Property	Monolith	Client-Server	Layered	Modular Monolith	Clean / Hexagonal / Onion	Pipeline (Pipe & Filter)	Batch Processing	Microservices	SOA	Event-Driven (EDA)	Actor Model	CQRS	Event Sourcing	Stream Processing	Space-Based	Peer-to-Peer
Deployment Unit	Single	Client + Server	Single	Single	Single/Multiple	Single/Multiple	Scheduled jobs	Multiple	Multiple	Distributed	Distributed actors	Single/Multiple	Single/Distributed	Distributed	Distributed	Fully distributed
Coupling	Tight	Medium	Medium	Medium	Loose	Loose	Loose	Loose	Medium	Loose	Very loose	Loose	Loose	Loose	Loose	Loose
Scalability	Low–Medium	Medium	Medium	Medium	Medium	High	High	High	High	High	Very high	High	High	Very high	Very high	Very high
Complexity	Low	Low	Low–Medium	Medium	Medium	Medium	Medium	High	High	High	High	High	High	High	High	High
Data Consistency	Strong	Strong	Strong	Strong	Strong	Depends	Strong (per batch)	Eventual	Mixed	Eventual	Eventual	Eventual	Eventual	Eventual	Eventual	Eventual
Typical Use Case	Small apps	Web apps	Enterprise apps	Growing apps	Maintainable, testable, domain-centric systems	Data processing	Reporting/ETL	Large systems	Enterprise integration	Reactive systems	Real-time concurrency	High-read systems	Audit/log systems	Real-time analytics	High-scale low-latency	Decentralized systems