Deciding Under Uncertainty
Bounding the downside and buying information cheaply.
4 to work through
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advanced
A decision must be made now and the information needed will not be available for six months. What should the approach be?
2 min answer -
advanced
A sponsor wants a date for a programme with several unknowns. Refusing to estimate is not an option. How do you handle it?
1 min answer -
advanced
An architectural decision must be made with genuinely insufficient information and the cost of delay is real. How should it be approached?
2 min answer -
advanced
An architecture decision must be made when the workload, scale and requirements are genuinely unknown. What approach works?
2 min answer
4 terms in this topic
Decision Under Uncertainty
Choosing when the information needed to be confident is unavailable, using the cost of being wrong rather than waiting for certainty.
practiceRecorded Assumption
Writing down the assumption a decision rests on, with the condition that would invalidate it - which converts an invisible dependency into a monitored one.
practiceSpike and Prototype
A time-boxed experiment run to reduce uncertainty about a specific question, producing evidence rather than a component.
practiceTrigger Condition
A specific, observable condition recorded alongside a decision that indicates it should be reconsidered - converting a point-in-time judgement into a…
Neighbouring topics
Architecture Decision-Making
General material on making and recording architectural decisions.
Architecture Decision Records
One decision, its context, alternatives and consequences, kept immutable.
Reversibility
One-way and two-way doors, and buying optionality deliberately.
Build vs Buy
Differentiation, five-year TCO, and the exit cost of each option.
Monolith vs Microservices
A team-topology decision far more often than a technology one.
SQL vs NoSQL
Decided by access patterns and query flexibility, not by data volume.
Sync vs Async
Whether the caller's outcome depends on the callee's response.
Strong vs Eventual Consistency
A per-operation decision, resolved by what a stale read would cost.
Managed vs Self-Managed
Trading control and unit cost against operational attention.
Serverless vs Containers
Spiky and event-driven versus sustained throughput.
Single vs Multi-Region
Driven by RTO, RPO and residency rather than by ambition.
Centralised vs Distributed
Shared platform leverage against team autonomy.
Performance vs Cost
Buying latency, and knowing what the last millisecond is worth.
Reliability vs Complexity
Mechanisms that add availability and add failure modes.
Security vs Usability
Varying control by the value of the action rather than uniformly.
Delivery vs Maintainability
Fast in the cheap places, careful in the expensive ones.
Trade-off Analysis Methods
ATAM, scenarios, and naming the points where qualities conflict.
Technology Selection
Evaluating options against drivers rather than against enthusiasm.
Decision Practice
Thresholds, review, supersession and keeping the log alive.