Some three-quarters of production deployments of open-source document-oriented Couchbase already involve replacing legacy relational systems, according to the NoSQL database company's CEO, Bob Wiederhold.
But that pattern of adoption has been piecemeal. Later in 2015, that picture should start to change.
"At the moment it's a relatively small number of applications and they're doing it more on an application-by-application basis," Wiederhold said. By the second half of next year that approach will alter to "a strategic, 'We're going to deploy this stuff in a very broad way'".
NoSQL database adoption can be seen as taking place in three overlapping phases, he said.
"Phase one started in 2008-ish, when you first started to see commercial NoSQL products being available. Phase one is all about grassroots developer adoption. Developers would go home one weekend, and they'll have heard about NoSQL, they download the free software, install it, start to use it, like it, and bring it into their companies," Wiederhold said.
"Generally, in phase one, people used it for lightweight applications - so internally-facing, fairly lightweight apps. We and MongoDB and DataStax certainly had a small number of customers that used us in the early days for mission-critical applications but those were few and far between."
Phase one was all about ease of development and the richness of the development environment, he said. Issues such as scalability and performance were less prominent because most of the apps involved were relatively small and did not have to operate at scale or provide high performance.
"Although there was a lot of grassroots developer adoption within companies all operating below the radar, enterprises are looking at all this and at some point they say, 'You know, I think NoSQL is feature-rich enough, it's reliable enough, it's stable enough that we can start to use it on our first few mission-critical business-critical apps.'"
At that point many businesses start to conduct deep strategic evaluations, something never undertaken in phase one. They stress-test scalability and performance, pick a winner and deploy.
"Whereas in phase one you saw a lot of $10,000, $30,000 or $50,000 deals, now in phase two you're seeing many hundred-thousand dollar deals, you're seeing million and multi-million dollar deals because obviously these mission-critical apps are operating at significant scale already. So they need to buy a lot of nodes and a lot of software to deploy," Wiederhold said.
The criteria for success changes dramatically in phase two because these are now mission-critical apps, supporting global audiences, so scalability, reliability and performance move to the fore.
"The key thing about phase two though is that the enterprises are starting to deploy NoSQL under their first few mission-critical applications. They haven't yet made the strategic decision to broadly deploy NoSQL. That's what we think phase three is about," he said.
"We think phase three is going to start probably in the second half of next year. It hasn't started yet. We're talking to some of our business customers. They're entering phase three. Of course, they don't call it phase three but they talking about, 'We want to broadly deploy NoSQL but before doing that we need these 14 features."
Wiederhold said many companies have the expertise to deal with NoSQL when it is deployed under only the first few mission-critical apps but a broad deployment of the technology requires a well-rounded product.
"In phase two they're doing their first two or three or maybe it's even 10. But what we hear a lot is what people ultimately want to do is they're spending $40m per year on Oracle and they're talking about 'OK, we're going to make a very significant shift'," he said.
"Not all at once but at some point they're going to say we're ready to begin our broad replatforming, our broad deployment of NoSQL. They're not going to completely replace Oracle but that's going to dramatically reduce what they pay to Oracle and that's going to be a much broader deployment."
It is inevitable that most database migrations are from relational to NoSQL rather than between NoSQL technologies, Wiederhold said.
"We absolutely are competing against the relational database incumbents. If you think about it, most of the world's mission-critical business-critical applications have been around a long time. They're not running on another NoSQL database today. They're running on a relational technology," he said
So in most cases Couchbase is replacing Oracle but also IBM, Microsoft SQL Server and MySQL.
"That's what we're replacing and in that sense that's who we're competing against. But when they do the evaluations, they're not evaluating the relational technology versus Couchbase or MongoDB or DataStax," Wiederhold said.
"They've already made a decision pretty much that they're going to use NoSQL for this specific application. Then it's just a matter of evaluating us versus Mongo versus DataStax - these days those are the three that they're usually evaluating."
Mountain View, California-based Couchbase describes itself as a 100 percent open-source company, with customers that include auction site eBay, e-commerce payments specialist PayPal, business social network LinkedIn, travel-industry technology firm Amadeus, and online gambling exchange Betfair.
In June Couchbase announced a series E investment injection of $60m, taking its total funding to $115m. The major Couchbase Server 3.0 beta was released in August, with the 3.0.1 first maintenance release available since October.
Couchbase Lite, a native NoSQL JSON database for mobile, went to general availability in May. Couchbase can be used as a document-oriented or pure key-value database and is available under the Apache 2.0 licence.