Below is a side‑by‑side comparison of OutSystems Cloud (PaaS) vs On‑Premises / Self‑Managed installations, focused on the aspects you listed.

1. Architecture

OutSystems Cloud

• Runs on OutSystems‑managed infrastructure in public cloud data centers (e.g., AWS/Azure).
• Uses the standard OutSystems layered architecture: IIS application servers, Platform Server, SQL/Oracle DBs, plus separate Platform, Log, and Session catalogs/schemas per environment, but all provisioned and operated by OutSystems. Infrastructure architecture and deployment options
• Typical infrastructure includes multiple environments (Dev, Test/QA, Prod, LifeTime) with front‑ends and DB servers sized according to the chosen edition (Basic/Standard/Enterprise). Infrastructure architecture and deployment options

On‑Premises / Self‑Managed

• Same logical architecture (Platform Server on IIS, Windows Server, SQL Server/Azure SQL/Oracle), but deployed on your own data center or IaaS (AWS/Azure) that you manage. Infrastructure architecture and deployment options
• You define and provision: number of front‑ends (standalone vs server farm), DB topology (shared vs dedicated instances), load balancers, and network segmentation. Infrastructure architecture and deployment options

Key Difference: Cloud uses the same technical stack, but the physical layout and capacity planning are pre‑designed and operated by OutSystems; on‑premises you decide and implement the architecture.

2. Administration & Operational Responsibilities

OutSystems Cloud

• OutSystems fully manages Platform Server, IIS, OS, and DB infrastructure: installation, upgrades, backups, platform services, and basic availability monitoring. OutSystems infrastructure
• You administer only applications and environments from the platform point of view (via Service Center and LifeTime): apps, deployments, users, roles, pipelines. OutSystems infrastructure
• OutSystems is responsible for monitoring and keeping the platform itself healthy, but not your app‑level performance/availability. Monitoring Web and Mobile Applications – Deployment Environments Monitoring

On‑Premises / Self‑Managed

• You manage everything below the platform: hardware, virtualization, OS, IIS, DB engine, storage, backups, DR, security hardening, and platform installation/configuration. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure
• You are responsible for monitoring all layers (network, OS, DB, platform services) and ensuring SLAs end‑to‑end. Monitoring Web and Mobile Applications – Deployment Environments Monitoring

Key Difference: Cloud offloads platform and infrastructure administration to OutSystems; on‑premises requires full operational ownership.

3. Deployment & Lifecycle Management

Both Models (Common)

• Use the same lifecycle: Dev → Test/QA → (UAT, optional) → Prod, plus a dedicated LifeTime environment. OutSystems infrastructure
• LifeTime centrally manages environments, apps, IT users, and cross‑environment deployment pipelines. Platform Overview – Application Lifecycle Management

OutSystems Cloud

• No initial platform setup; OutSystems provisions environments and sends access credentials. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure
• You configure teams and permissions in LifeTime, but infrastructure pipelines (e.g., Basic/Standard/Enterprise) usually follow predefined patterns (number of environments, front‑ends, DB topology). Infrastructure architecture examples – Basic/Standard/Enterprise edition

On‑Premises

• You must install the Platform Server, configure LifeTime, define environments, and optionally create multiple pipelines for different app portfolios and NFRs (e.g., extra UAT, special HA). Infrastructure architecture – Pipelines
• Full flexibility to add or change environments (e.g., separate UAT or security‑isolated pipeline) as long as your infrastructure supports it. Infrastructure architecture – Pipelines

Key Difference: Cloud gives you ready‑made environments and pipelines; on‑premises you explicitly design and implement the environment topology.

4. Security

OutSystems Cloud

• OutSystems implements and maintains infrastructure security controls (patching, network isolation, secure configuration) for the platform components. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure
• You focus on application‑level security: roles, authentication, authorization, data model, and app logic. Infrastructure architecture – OutSystems services and Server.Identity

On‑Premises

• You must secure all layers: network firewalls, OS hardening, IIS security, DB security, encryption, backup protection, and compliance controls. Infrastructure architecture – Deployment options
• You can design stricter data‑segregation architectures (e.g., dedicated DBs for sensitive pipelines, separate network segments) to meet internal compliance or regulatory requirements. Infrastructure architecture – Pipelines and data segregation

Key Difference: Cloud delegates infra security to OutSystems; on‑premises lets you tailor security deeply but requires you to manage and prove it.

5. Performance & Scalability

Common Platform Behavior

• Platform generates standard .NET server code and HTML/CSS/JS clients, running on IIS and relational DBs in both models. Infrastructure architecture – Standard, reliable technologies
• Performance logs are stored in dedicated Log DB catalogs/schemas (OSLogs) to avoid impacting the main app DB. Monitoring Web and Mobile Applications – Data Access and Performance Considerations

OutSystems Cloud

• Scalability (additional front‑ends, HA, DB replicas) is provided as part of the chosen edition:
  • Basic: simpler setup, 3 environments, minimal HA. Infrastructure architecture examples – Basic edition infrastructure
  • Standard/Enterprise: more environments, more front‑ends, HA with multiple DCs and DB standby for mission‑critical apps. Infrastructure architecture examples – Standard/Enterprise
• OutSystems manages horizontal scaling in the cloud, but you may need to coordinate with them for major capacity changes.

On‑Premises

• You control when and how to scale:
  • Standalone configuration: single front‑end, typical for non‑production. Infrastructure architecture – Standalone configuration
  • Server farm: multiple front‑ends with load balancer, multiple queues, typically for production and high load. Infrastructure architecture – Server farm configuration
• You choose DB scale‑up/scale‑out (dedicated servers, replicas, storage tiers) and can have different HA strategies per pipeline. Infrastructure architecture examples – Enterprise edition infrastructure

Key Difference: Cloud scalability is packaged/managed by OutSystems; on‑premises scalability is fully customizable but also fully your responsibility (capacity planning, load balancing, HA).

6. Maintenance (Upgrades, Backups, Patching)

OutSystems Cloud

• Platform upgrades, patching, and infrastructure maintenance are done by OutSystems as part of the service. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure
• Automatic backups and DR are provided by OutSystems, according to their cloud SLAs. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure

On‑Premises

• You perform platform server installation/upgrade, OS patching, DB patching, and backup/restore procedures. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure
• You must ensure your hardware and software meet system requirements, and that permissions are correctly set for file system changes, services execution, and DB modifications before installation/upgrades. OutSystems infrastructure – Cloud vs Self-Managed Infrastructure

Key Difference: Cloud: “managed PaaS” model; On‑Prem: “you build and maintain the platform” model.

7. Monitoring & Operational Responsibilities

OutSystems Cloud

• OutSystems monitors and keeps the platform components running; however, application performance and availability monitoring remains your responsibility. Monitoring Web and Mobile Applications – Deployment Environments Monitoring
• You use Service Center, LifeTime Analytics, Performance Monitoring API, and external tools (Elastic Stack, AppDynamics, Dynatrace, etc.) via Forge components to monitor apps and define SLAs (slow queries, error rate thresholds). Monitoring Web and Mobile Applications – Monitoring Tools and Performance Monitoring API

On‑Premises

• Same platform monitoring tools are available, but you additionally need to monitor servers, DB, network, and all middleware. Monitoring Web and Mobile Applications – OutSystems Platform Monitoring
• On‑premise customers are fully responsible for monitoring “all technology layers” supporting the platform. Monitoring Web and Mobile Applications – Deployment Environments Monitoring

Key Difference: In Cloud, OutSystems covers platform health; in On‑Premises, you cover platform + underlying stack.

Summary

• Architecture: Same logical stack (.NET/IIS/DB) but OutSystems Cloud is pre‑architected and operated; On‑Premises is tailor‑made and self‑operated.
• Administration & Ops: Cloud offloads infra/platform admin to OutSystems; On‑Prem requires full ownership.
• Deployment & Lifecycle: Both use LifeTime and pipelines; Cloud gives ready‑made environments, On‑Prem gives full design freedom.
• Security: Cloud = OutSystems‑managed infra security, you secure apps; On‑Prem = you secure infra + apps.
• Performance & Scalability: Cloud scalability packaged by edition; On‑Prem scalability fully under your control (and responsibility).
• Maintenance: Cloud handles upgrades/backups/patches; On‑Prem you handle all maintenance.
• Monitoring & Responsibilities: Cloud: OutSystems monitors platform, you monitor apps; On‑Prem: you monitor everything.