Public cloud continues to go up and up: according to Gartner, the market will grow 21.4% in 2018 to total $186.4 billion (£131.4bn).

Almost 40% of this will come from software as a service (SaaS), with a quarter to come from what Gartner calls cloud business process services (BPaaS) – delivering business process outsourcing (BPO) – and 22% to come from infrastructure as a service (IaaS).

IaaS, however, will outstrip BPaaS by 2021 according to Gartner’s predictions. In three years total public cloud service revenues will surpass $300 billion ($302.5bn), with SaaS accounting for 38% of that total, IaaS 27% and BPaaS 19%. SaaS will also hit 45% of total application software spending by 2021.

When it came to analysing IaaS specifically, Gartner predicts the hyperscale players to increase their dominance. In 2016, the analyst firm said the top 10 players in the market – Amazon Web Services (AWS), Microsoft Azure, Google, IBM and the rest – accounted for half of the total IaaS market. By 2021, this figure will rise to 70%.

“The increasing dominance of the hyperscale IaaS providers creates both enormous opportunities and challenges for end users and other market participants,” said Sid Nag, Gartner research director. “While it enables efficiencies and cost benefits, organisations need to be cautious about IaaS providers potentially gaining unchecked influence over customers and the market.”

Nag noted the rise of multi-cloud as key to this. Organisations will want to move workloads from cloud to cloud without fear of reprisal. Could there be another wave of vendor lock-in? “In response to multi-cloud adoption trends, organisations will increasingly demand a simpler way to move workloads, applications and data across cloud providers’ IaaS offerings without penalties,” said Nag.

Platform as a service (PaaS) will comprise 8% of the total public cloud market this year at a relatively princely $15 billion, while cloud management and security services will total $10.5bn.