Build vs Buy
Differentiation, five-year TCO, and the exit cost of each option.
4 to work through
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beginner Multiple choice
A four-person startup needs SMS phone verification at signup - roughly 20000 messages a month to US numbers. One engineer proposes sending directly through a carrier gateway rather than paying a provider such as Twilio. Which fact should decide it?
3 min answer -
intermediate Multiple choice
A platform must decide whether to build or buy a capability. What is the primary test, and what is the pattern that usually works?
2 min answer -
intermediate
A team proposes building an authentication service rather than buying one, arguing it is two weeks of work. Respond.
2 min answer -
advanced
Your company needs a feature flag and experimentation platform. A vendor charges a substantial annual fee; a team estimates six weeks to build one. Decide.
2 min answer
3 terms in this topic
Build-vs-Buy Total Cost
Comparing a purchased solution against building one on the full lifetime cost, including the maintenance and opportunity costs that estimates omit.
practiceDifferentiation Test
The question of whether a capability is a source of competitive advantage, used as the primary filter in build-versus-buy decisions.
metricExit Cost
The engineering effort and elapsed time required to move off a vendor, which sets both the real price of lock-in and the team's negotiating position …
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.
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.
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.