Performance vs Cost
Buying latency, and knowing what the last millisecond is worth.
5 to work through
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intermediate
A team can make a workload ten times faster by tripling its infrastructure cost. What determines whether that is worth it?
2 min answer -
intermediate
Finance asks why your services run at 55% utilisation rather than 90%. What is your answer?
2 min answer -
intermediate
Finance offers to fund a three-year committed-use discount covering most of the compute bill in exchange for a locked instance family and quantity, and engineering agrees. What has the architecture given up, and when does that bill arrive?
3 min answer -
advanced
A streaming platform can halve latency by doubling infrastructure cost. How should this trade-off be evaluated?
2 min answer -
advanced
Alibaba reported a peak of 583000 orders per second during Singles' Day 2020, far above its ordinary daily rate. A retailer with a 40x annual peak asks whether it should provision for peak all year, since that is what the big platforms clearly do. What did a platform in that position actually buy, and where does copying it go wrong?
2 min answer
3 terms in this topic
Cost Per Transaction
Infrastructure cost divided by business volume, which reveals efficiency trends that absolute spend conceals.
metricLatency Revenue Elasticity
The measured change in a business outcome per unit of added or removed latency, which turns "faster is better" into an amount of money and tells you …
conceptPerformance versus Cost
The trade between latency and spend — where headroom is the mechanism and high utilisation is the false economy.
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.
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.
Deciding Under Uncertainty
Bounding the downside and buying information cheaply.
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.