ce level objective (SLO; see <a data-type="xref" href="http://fakehost/sre/sre-book/chapters/service-level-objectives">Service Level Objectives</a>). Many years ago, the Bigtable service’s SLO was based on a synthetic well-behaved client’s mean performance. Because of problems in Bigtable and lower layers of the storage stack, the mean performance was driven by a &#34;large&#34; tail: the worst 5% of requests were often significantly slower than the rest.
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