What an SLA actually buys you

An SLA is negotiated by procurement and lawyers, filed, and then read properly for the first time by an engineer at three on a Sunday morning while something is on fire. That reading is the only one that counts. Most of the document survives it badly.

What the clock is measuring

Response time and restoration time are different promises, and only one of them describes the outage. Acknowledgement is the cheapest target in the industry to hit, because an automated reply satisfies a fifteen-minute response commitment without a human being awake. Restoration time is what the business experiences. Ask for both. Expect the restoration figure to be softer and negotiated harder, which is a reasonable signal about which one the supplier believes is real.

Check when the clock starts. If it starts when a ticket is raised, and tickets can only be raised through a portal that shares infrastructure with the platform, then the clock is unreliable in precisely the circumstances it was written for. A phone number that reaches a human is old technology and it still works.

The exclusions do the real work

A 99.9% commitment with a long exclusions list is a weaker promise than 99.5% with a short one, and the percentage on the cover page is what gets compared in the evaluation matrix. Scheduled maintenance, third-party dependency, anything caused by the client, anything beyond reasonable control. If failures at the cloud provider are excluded and the platform sits in a single region of a single provider, the commitment covers a narrower set of events than anyone in the procurement meeting believes.

Read the exclusions before the number, then work out which real incidents from the last two years would have fallen inside the agreement. That exercise takes an afternoon and it is more informative than the whole schedule of credits.

Availability of what, exactly

Component uptime and service availability diverge constantly. A health endpoint returning 200 while payments fail is an available system by one definition and an outage by any definition the business recognises. Define availability as a named business transaction completing within a named time: a payment settling, a citizen filing a return, a ticket being raised. Measure it with a synthetic transaction run from outside the estate, and agree who runs the measurement. A supplier measuring its own availability from inside its own network reports different numbers to a probe sitting where the users are, and both parties will believe their own instrument.

Severity written in the language of the business

Severity definitions drafted by the supplier tend to describe systems. Severity 1 means total loss of service. At three in the morning that sentence generates an argument, because the system is up and only one function is broken. Definitions drafted by the business describe consequences: no payment can settle, no vehicle can be dispatched, no request can be logged. Written that way, severity becomes a lookup rather than a negotiation, and the negotiation is the expensive part of the night.

The clause that matters most

Service credits are the part everyone spends the longest on and they almost never compensate for the incident. What genuinely has value is the obligation that a named person, with the access and the authority to act, is reachable within a stated time. Alongside it, write down the standing authority: what an on-call engineer is permitted to do during a severity 1 without prior approval, and what must be reconstructed and reviewed afterwards. Without that clause, the restoration clock runs while somebody tries to find a change approver on a Sunday, and the SLA has bought a delay it also charges for.

On the internal service desk we built for Tata Realty and Infrastructure, every request lands against an SLA clock with a route and an owner. The value in that was never a percentage. It was that nothing could be raised and then quietly go missing. An agreement nobody can dispute at three in the morning is worth more than an impressive figure on the cover.