Operations → Reliability
SLA
An external agreement about service availability, performance, or support expectations.
Motivation
SLA exists because teams need a practical way to solve a recurring problem in real systems. It gives engineers a shared abstraction for discussing trade-offs instead of treating every implementation as unique.
Where it fits
SLA belongs to the operations track in the reliability layer. It is useful when reasoning about nearby concepts such as SLO, Availability.
Mental model
Think of SLA as a named design pressure: it usually improves one quality, such as scalability, safety, usability, or operability, while adding constraints that must be understood.
Example in practice
When SLA appears in a system, the important question is not only what it is, but why the system needs it and what failure modes it introduces.
Common mistakes
- Using SLA because it is fashionable rather than because the problem requires it.
- Ignoring the operational cost or learning curve.
- Treating the concept as isolated instead of connecting it to neighboring concepts.