The key point here would be how you are measuring the downtime and what that means. From a technical perspective it's easy as there's many CDNs that can deliver that kind of reliability very inexpensively. So I view this as less a technical exercise and more a contractual one.
You'd need to determine very precisely how you measure the SLA, if there's any exclusion periods (maintenance), and what the penalty is for violation. With an SLA like that the site simply being slow to load may constitute a violation.
Comments
The key point here would be how you are measuring the downtime and what that means. From a technical perspective it's easy as there's many CDNs that can deliver that kind of reliability very inexpensively. So I view this as less a technical exercise and more a contractual one.
You'd need to determine very precisely how you measure the SLA, if there's any exclusion periods (maintenance), and what the penalty is for violation. With an SLA like that the site simply being slow to load may constitute a violation.