Trade-off Fundamentals
Why every architecture is a set of purchases, and how to state what you gave up.
4 to work through
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intermediate
A user-generated storytelling platform is 98% reads with an extremely skewed popularity distribution. The team debates caching, read replicas and denormalisation. How should the trade-off be framed?
2 min answer -
intermediate
An architecture review proposes multi-region active-active, event sourcing, CQRS and a service mesh for an internal tool with 500 users. Write the simpler architecture, and state the specific facts that would justify each rejected pattern later.
2 min answer -
advanced
A file-sync company moves the bulk of its storage from a public cloud onto its own infrastructure. What was gained, what was sacrificed, and under what conditions would this trade-off be wrong for a different company?
2 min answer -
advanced Multiple choice
An organisation decomposed into thousands of microservices during hypergrowth and later consolidated into coarser domain groupings. Was the original decision wrong?
2 min answer
3 terms in this topic
Reversibility
The property of a decision that determines how much analysis it deserves, since a cheaply reversible choice can be tested rather than debated.
conceptSecond-System Effect
The tendency for a replacement system to accumulate every capability the first one lacked, producing something more complex than either the old syste…
conceptTrade-off Fundamentals
Every architecture is a set of purchases; the skill is naming what was bought, what was sold, and at what exchange rate.
Neighbouring topics
Architecture Fundamentals
General material on what solution architecture is and what an architect is accountable for.
Requirements to Constraints
Turning stated requirements into the constraints that actually bound a design.
Functional vs Non-Functional
Behaviour versus quality of behaviour, and why only the second constrains structure.
Architectural Drivers
The small subset of requirements whose change would force the structure to change.
Quality Attributes
Availability, latency, throughput, security, cost — expressed as testable scenarios.
Architecture Principles
Durable agreed rules that rule options out, stated with rationale and implications.
Coupling
How much one component must know about, or change alongside, another.
Cohesion
Whether the things inside a boundary belong together and change for the same reason.
Modularity
Composing a system from parts that can be understood and replaced independently.
Separation of Concerns
Organising so that a change to one concern touches one place.
Abstraction & Encapsulation
Hiding mechanism behind contract, and protecting invariants by owning state.
Architecture Styles
System-level organising shapes, and how they differ from problem-level patterns.
Evolutionary Architecture
Designing for guided incremental change rather than for correctness on day one.
Fitness Functions
Automated checks that an architectural characteristic still holds.
Architecture Documentation
What to write down, at what altitude, and what nobody will ever read.
Conway's Law
Systems mirroring the communication structure of the organisation that builds them.
Technical Constraints
Existing estate, skills, licences and platforms as inputs rather than obstacles.
Architecture Roles
Solution, enterprise, domain and platform architecture, and where each is accountable.
Reference Models
Shared conceptual frames — layering, tiers, viewpoints — and their limits.