Answers
What is an SLI, SLO and SLA?
In short
An SLI measures something (e.g. availability), an SLO is your internal target for that SLI (e.g. 99.9%), and an SLA is the contractual commitment you make to customers — usually weaker than your SLO.
Short answer
An SLI measures something (e.g. availability), an SLO is your internal target for that SLI (e.g. 99.9%), and an SLA is the contractual commitment you make to customers — usually weaker than your SLO.
What this actually means in practice
SLIs should reflect user experience, not just system health. SLOs drive engineering priority — error budgets translate them into release decisions. SLAs are legal artefacts and should never be tighter than your SLOs.
The most common pitfall
Marketing-team SLAs that engineering cannot defend.
What to do next
Define SLIs from user journeys before negotiating any SLA.
Frequently asked questions
Does Forth Systems help with this?
Yes — Forth Systems works with banks, payment institutions, insurers and infrastructure operators on exactly this kind of work. Engagements start with a fixed-scope assessment so you see the shape before committing.
How experienced is the team?
Engagements are staffed by named, UK-based senior engineers — not a rotating offshore pool. References from the second line of comparable clients are available on request.
Where are you based?
Edinburgh-based, delivering UK-wide with onsite presence in London and across Scotland as required.
How fast can we start?
Most engagements start within 2-4 weeks of a signed SoW, faster where an existing supplier framework is in place.