What Is Platform as a Service? Understanding Cloud-Based PaaS Examples, Benefits & More

For enterprises with mainframe or IBM i, PaaS accelerates app delivery—but legacy modernization succeeds when you change one boundary at a time: decouple → coexist → migrate. That approach reduces risk and keeps mission-critical channels online.

Digital transformation is something that all enterprises must take seriously to futureproof their organizations. In many cases, cloud modernization plays a key role in that transformation and, as such, it’s critical to understand Platform as a Service (PaaS), as well as other cloud service delivery models.

What is Platform as a Service?

Platform as a Service (PaaS) is a managed application platform, runtime, language frameworks, and DevOps tooling delivered over the cloud so teams can build, deploy, and run apps while the provider manages infrastructure. Security and compliance are shared responsibilities: the provider secures the platform; you secure your code, data, identities, and configurations.

PaaS vs SaaS vs IaaS: Understanding the place of PaaS in cloud computing

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So, that’s the PaaS meaning covered, but it’s also important to understand that it’s far from alone in terms of cloud service delivery models. The best way, therefore, to grasp the place of Platform as a Service in cloud computing terms is to compare it directly with Infrastructure as a Service (IaaS) and Software as a Service (SaaS).

PaaS, SaaS, and IaaS all provide organizations with access to cloud resources over the internet. The principal difference lies in who has responsibility for and control over the management of which resources.

In the case of PaaS, your provider manages the infrastructure required for application development. You then have the ability to build, deploy, and manage applications.

SaaS is more of a “plug and play” scenario. When you invest in a SaaS solution, you get fully managed and hosted software that you don’t even need to install. Typically, you simply log in and get access to the full features of the solution.

Finally, IaaS is a delivery model that offers access to “raw” IT infrastructure, such as compute, storage, networking, and virtualization. You then manage and handle everything else.

Practical tip: favor portability (12-factor practices, containers, open standards) to reduce long-term lock-in as your architecture evolves.

Cloud Platform as a Service examples

PaaS isn’t a brand-new concept or offering. There is a selection of suppliers who have been providing PaaS services and solutions to businesses for a number of years. Some of the best-known examples of PaaS include:

Google App Engine

GAE allows you to build large server-side websites and supports your DevOps team with a range of easy-to-use developer tools. GAE also supports a variety of programming languages, including Java, Node.js, Go, Ruby, Python, and PHP. GAE offers a fully managed environment, so your team can focus on code while the platform manages all cloud infrastructure concerns.

Microsoft Azure

Microsoft (Windows) Azure is another platform that lets you divert attention from running your infrastructure by migrating your servers to the cloud and going serverless. You can also add hybrid capabilities by combining on-premises architecture with cloud-based architecture or running all your workloads on Azure.

AWS Elastic Beanstalk

Elastic Beanstalk helps organizations easily deploy and scale all their web applications and services. Your developers simply upload their code, and EB automates all aspects of deployment, from load balancing and capacity provisioning through to auto-scaling and monitoring.

These offerings are managed platforms for web/app workloads rather than integration layers for legacy systems.

How do PaaS services work?

PaaS solutions, then, are often leveraged for software and app development by businesses. They abstract the infrastructure complexities and give developers the room to focus on actually building and iterating apps and software.

The three main components of a PaaS solution are:

• Cloud infrastructure - This can include virtual machines (VMs), data centers, storage, and more.
• Software - operating systems, development kits, and similar examples for building, deploying, and managing applications.
• User interface - Somewhere for developers to work. This may be a graphical user interface (GUI), a command line interface (CLI), an API interface, or all three.

PaaS speeds net-new development; when legacy modernization is required, teams typically expose core functions as well-governed APIs rather than pushing more traffic through generic middleware.

Benefits of PaaS

What, then, makes PaaS attractive to businesses looking to modernize their tech infrastructures? There are a range of PaaS benefits that combine to provide the answer:

Time-savings

If you’re using PaaS, then your DevOps team can build applications much faster than if they were working on traditional platforms and backend architecture. PaaS provides developers with a totally virtual software environment that allows them to code, test, and deploy applications faster and streamline workflows.

Scalability

Every business wants to grow. The problem with outdated physical IT infrastructure is that it has limitations when it comes to scalability. In most cases, growth means costly expansion of physical IT infrastructure and computing resources, as well as ongoing maintenance costs. PaaS allows you to scale up or down according to your business needs.

Easier maintenance

Because they’re operating in the cloud, your developers can build applications without having to build, configure, or update physical servers. Your PaaS provider shoulders responsibility for platform maintenance and upgrades, so this takes those roles away from your IT team.

Accessibility

There are two sides to this benefit. The first is that many PaaS vendors offer options for application development across different platforms, such as mobile devices, various browsers, and computers. This makes it easier for your DevOps team to work on cross-platform apps simultaneously.

The second aspect is that, in a world where remote or hybrid-working models are common, the fact that PaaS is cloud-based means that you can have several developers working on the same project even when they’re in different geographical locations.

Cost-savings

PaaS can reduce run and tooling costs via pay-as-you-go and managed services, though actual savings vary by workload mix, scale, and governance.

For legacy-heavy estates, pair PaaS with decoupled APIs so app teams move fast without adding brittle integration layers.

Types of PaaS

Not all PaaS offerings are the same. The right choice depends on how much control you need, where your workloads can run, your compliance posture, and how portable you want your applications to be over time. The landscape breaks down into core PaaS models and a few specialized categories.

Core PaaS models

Public PaaS

Use when you want speed and a fully managed platform on a public cloud. You control your apps and configurations; the provider manages the platform services.

• What it’s good for: rapid delivery of web and API workloads, elastic scaling, pay-as-you-go.
• Trade-offs: less control over underlying infrastructure; be deliberate about portability to avoid lock-in.

Private PaaS

Run a PaaS inside your private cloud or data center for tighter control and compliance while giving teams a modern developer experience.

• What it’s good for: regulated environments, data residency, custom policies and network controls.

• Trade-offs: more to operate and maintain; capacity planning is on you.

Hybrid PaaS

Blend public and private PaaS to place workloads where they fit best (e.g., sensitive systems on-prem, burst or new digital on public cloud).

• What it’s good for: gradual cloud adoption, mixing steady and seasonal demand, jurisdictional needs.

• Trade-offs: added complexity in governance, observability, and lifecycle management across environments.

Specialized categories

CPaaS (Communications PaaS)

Adds real-time communications to apps via APIs/SDKs (voice, video, messaging, authentication).

• Use when: you need communications features without building telecom infrastructure.

MPaaS (Mobile PaaS)

Low-code and toolchains focused on building and shipping mobile applications.

• Use when: mobile delivery speed and consistent app services (auth, notifications, storage) matter most.

Open PaaS

Open-source platforms (for example, Cloud Foundry or Kubernetes-based stacks) that give you PaaS-like developer workflows with stronger portability.

• Use when: you want to reduce lock-in and standardize workloads across multiple clouds or on-prem.

Related but different: iPaaS (integration platform as a service) brokers and mediates traffic between systems. It’s not the same as PaaS, which is focused on building and running applications. For legacy estates, teams typically expose core functions as well-governed APIs rather than pushing more traffic through generic middleware.

A note for legacy and regulated environments

If you run mainframe or IBM i, validate how your chosen model will work alongside stateful transactions and domain-specific protocols (3270/5250, MQ/CTG/IMS Connect, copybooks/EBCDIC, Db2 for z/OS types). A low-risk path is to decouple a clear boundary, run in coexistence while redirecting traffic to cloud services, and migrate domain by domain with rollback available.

How to choose a PaaS provider

Selecting a PaaS is ultimately about more than developer speed. The right choice balances day-to-day productivity with the controls you need for security, compliance, and long-term portability.

Start with workload fit languages and frameworks you use now, the application models you rely on (web APIs, background jobs, scheduled tasks), and the data services you expect to pair with your apps. From there, look at the developer experience the platform provides: paved-road pipelines, sensible defaults, and self-service that makes new environments quick to create but easy to govern.

Security and compliance should be assessed as a shared-responsibility model. Confirm single sign-on and fine-grained access controls, encryption in transit and at rest, key management options, and how the platform supports auditability and export of logs to your existing observability stack. Networking matters as much as runtimes: private connectivity (peering or private endpoints), ingress controls and rate limiting, and clear egress visibility reduce surprises later.

If you run significant legacy workloads—especially on z/OS mainframe or IBM I evaluate how a candidate PaaS will coexist with those systems while you modernize. Many mission-critical processes are stateful (for example, CICS/IMS units of work or IBM i commitment control), and not every stateless pattern maps directly. Protocols and data formats such as 3270/5250, MQ, CICS Transaction Gateway, IMS Connect, copybooks/EBCDIC/packed decimals, and Db2 for z/OS types may not be first-class in generic connectors. Ask how the platform helps protect upstream systems with back-pressure, circuit-breaking, and throttling, and how it supports safe cutovers with session affinity, idempotency, and rollback.

This is also where OpenLegacy fits into a PaaS decision without changing what PaaS is. OpenLegacy isn’t a PaaS or an iPaaS; it focuses on connecting directly to core systems and generating well-governed APIs from legacy assets such as COBOL/RPG programs, CICS/IMS transactions, and data structures defined in copybooks. That approach lets teams decouple a clear boundary, keep existing 3270/5250 channels and operations online in a coexistence phase, and then migrate domain by domain at their own pace. It also reduces dependency on heavy, generic middleware by standardizing how legacy capabilities are exposed to the PaaS layer your developers already use.

A practical way to validate fit is to ask for a reference architecture for your scenarios such as networks, identities, data flows, observability, and to run a small pilot with measurable outcomes. For organizations with legacy estates, the most reliable path is phased: decouple, coexist, and then migrate, using the PaaS where it helps you move faster while keeping mission-critical systems available. 

Where OpenLegacy Fits with PaaS Strategies

PaaS speeds how teams build and run applications; the harder part is connecting critical systems safely while you evolve the architecture. OpenLegacy isn’t a PaaS or an iPaaS. It sits alongside your platform as a governed connectivity layer that turns core system capabilities into consistent, modernization-ready APIs so you can move at cloud speed without betting the business on a big-bang rewrite.

If you do have legacy systems (for example, mainframe or IBM i), OpenLegacy provides a practical path forward. We start by analyzing dependencies to identify clean decoupling points, then generate and standardize APIs directly from legacy assets (such as COBOL/RPG programs, CICS/IMS transactions, and copybook-defined data). That lets you run in coexistence—keeping 3270/5250 channels and operations online—while you redirect traffic gradually to new services and keep rollback available. Because connectivity is direct and governed, you avoid piling on generic middleware and reduce long-term lock-in: the APIs you expose to your PaaS are portable and predictable as you retire technical debt domain by domain.

If you don’t run legacy today, the same patterns still help. Standardizing how back-end capabilities become APIs gives you portability across clouds and vendors, smoother cutovers between versions of services, and a cleaner path for inevitable complexity; M&A integrations, packaged app upgrades, data residency changes, or adopting new runtimes. In other words, the decouple-first approach that protects legacy estates also future-proofs cloud-native ones by keeping your application layer loosely coupled to whatever powers it behind the scenes.

Bottom line: OpenLegacy complements your PaaS by making the “hard parts” of integration safer and more consistent. Whether you’re modernizing mainframe/IBM i or building net-new cloud services, the same discipline applies, decouple → coexist → migrate, so you can deliver faster without compromising governance or uptime.

PaaS FAQs

What does PaaS stand for?

PaaS stands for Platform as a Service. It’s a cloud service delivery model that gives developers the infrastructure they need to build, deploy, and manage applications. That makes it a beneficial choice for enterprises looking to modernize legacy systems and harness the benefits of cloud computing.

What are some PaaS security best practices?

When working with a PaaS provider, one of the most important best practices for security purposes is to fully understand how the solution works and what you need to do to protect your data. Ask the provider about the access controls they provide, encryption they use, and what their redundancies are in case of disaster recovery.

Which PaaS company should you choose?

While there are many Platform as a Service providers available for you to choose from, what’s best for your business may not necessarily be what’s best for others. Therefore, it’s vital that you carefully plan which option is best for your needs.

This means that, as well as looking at your current needs, you should also consider your future needs and what each provider brings to the table.

One thing you should always consider is what you’re moving from and what you want to move to. If you’re operating an outdated legacy system and want to migrate to the cloud, then it’s important that you think about everything that entails.

If you’re modernizing your technology stack, then you’ll be thinking a lot about flexibility and customization. These are things that can be achieved through microservices architecture networks with API-powered connections.

How does PaaS change when you have mainframe or IBM i systems?

PaaS accelerates app delivery, but legacy estates introduce constraints—stateful transactions (CICS/IMS; IBM i commitment control), protocol/data gaps (3270/5250, MQ/CTG/IMS Connect, copybooks/EBCDIC, Db2 for z/OS), and governance (RACF/ACF2, audit, residency). A low-risk route is to decouple legacy functions as secure APIs, run in coexistence, then migrate domain by domain. 

What’s the difference between PaaS and iPaaS—and where does OpenLegacy fit?

PaaS is a runtime platform for building and running apps. iPaaS is an integration broker that routes/mediates traffic between systems. OpenLegacy is neither—it connects directly to core systems to produce governed APIs that reduce dependency on heavy ESB/iPaaS and make modernization safer.