Parallel ESI is a performance-enhanced version of open source ESI. Parallel ESI issues all the ESI includes in parallel, upfront, so a single slow include does not slow down other operations. Open source ESI processes includes serially, one command at a time. If a single include is slow, the whole delivery pipeline is stalled.
The dominance of e-commerce in the world of retail surged over the past two decades to the point that online shopping is a regular part of daily life, often surpassing real-life retail experiences in convenience, cost and even immediacy: you can find exactly what you want online (no guarantees at your local shop) and have it shipped to you, and in some cases, have it in hand the same or next day. All from the comfort of home, office or wherever you happen to be. I think we’re all pretty used to this.
At this point, it’s probably true to state that you haven’t got much of an e-commerce or media service if you aren’t personalizing content for every individual user. That is, in your efforts to engage users, create customers, promote stickiness, boost numbers of completed transactions and content consumption and foster return visits, repeat purchases or subscriptions to your site, you’ve already made every effort to make content suggestions and recommendations to suit their demonstrated interests, habits and behavior. This is all fairly standard and expected stuff.
Mobile web performance is key to meeting the accelerating proliferation of mobile as one of, if not the, most used devices in users’ hands. Cisco’s Visual Networking Index predicts that by 2020, smartphone traffic will even surpass PC traffic. While this inevitability unfold, another uncomfortable inevitability is the growing pains that go hand in hand with proliferation. Users expect instantaneous results - waiting time will drive users away: Google research concluded that “when your site or app is clumsy or slow, 29% of smartphone users will immediately switch to another site or app (...). In fact, of those who switch, 70% do so because of lagging load times.”