SLA

A service level agreement: a provider's contractual commitments to uptime and performance, with remedies when they are missed.

An SLA is a promise with a penalty clause. It defines the measurable service levels, usually uptime percentage over a month, sometimes response and resolution times, and what the customer receives when the provider misses: service credits, contractual exit rights, or nothing beyond apology, depending on the agreement. The percentages are quoted by nines: 99.9 percent monthly uptime allows about 43 minutes of downtime, 99.99 percent about 4.4, and the allowed minutes fall tenfold per nine while the engineering cost of each nine rises steeply.

Why it matters to an indie builder: you consume SLAs and you make them. As a consumer, the SLA plus the status-page history tells you what a provider's word is worth, a 99.9 percent commitment with a real credit remedy and a clean incident history is a contract, a 99.99 percent badge on a marketing page with a remedy of sorry is decoration. As a provider, the moment an enterprise customer's security review arrives, availability commitments become a negotiation, and pricing them honestly, credits proportional to fees, exclusions for scheduled maintenance, is how small vendors pass procurement without betting the company.

A concrete example: a $900 monthly SaaS depends on a $20 search provider. During a March outage the provider misses its 99.9 percent SLA by six hours. The remedy in its terms: 10 percent of that month's fees, a $2 credit against demonstrable lost revenue and customer anger. The lesson is arithmetic, not outrage: the provider's penalty and your damage differ by two orders of magnitude, so the actual protection is architectural, a caching layer that degrades gracefully when search fails, preserving 90 percent of the experience. The SLA covers the invoice; the design covers the business.

Common mistakes: reading the headline number and not the measurement window, exclusions and remedy (three documents, all of which matter), promising nines you cannot engineer before you have the observability to detect misses in real time, treating scheduled maintenance windows as free (customers experience them identically to outages; minimize and announce), and quoting internal targets to customers as if they were contractual commitments, which is how marketing copy becomes a legal liability.