Public vs Private Cloud: what actually differs, in plain English
Choosing between public cloud and private cloud isn’t a matter of faith; it’s about control, risk and how you want to run your infrastructure. Here’s a pragmatic, UK-friendly breakdown to help you decide.
Simple definitions
Public cloud: Shared platforms (multi-tenant) where you rent compute, isolated storage and networking on demand. You trade some control for elasticity and speed.
Private cloud: Dedicated environment (single tenant) where your organisation controls the stack, location and change cadence. You trade some elasticity for sovereignty and custom policy.
Economics & cost model
Public cloud: Opex-led, pay-as-you-go. Brilliant for bursty workloads, pilots and unpredictable growth. Watch egress, premium services and “always-on” instances—right-size or automate shutdown.
Private cloud: Predictable spend and better unit economics at steady state or high utilisation. Hardware lifecycle and capacity planning sit with you (or your provider) but can reduce total cost for stable workloads.
Security, data & compliance
Public cloud: Strong shared-responsibility model and rich security services out of the box. Data residency depends on region choice; auditors will expect you to prove controls.
Private cloud: Tighter data locality and change control, simpler stories for sensitive records, and custom network segmentation. You still need robust process: backups, DR, patching and monitoring don’t do themselves.
Performance & control
Public cloud: Rapid access to specialised services. Performance is excellent but noisy neighbours and service limits can appear in extreme cases.
Private cloud: Consistent performance and bespoke tuning (CPU types, storage tiers, network QoS). Ideal for latency-critical apps and fixed SLAs across your infrastructure.
Scale & agility
Public cloud: Near-instant scale; global reach in minutes. Perfect for seasonal spikes, experiments and go-to-market speed.
Private cloud: Scales on planned capacity. Change windows and governance are yours to set—useful when stability beats speed.
Operations & skills
Public cloud: Faster to start; deep catalogue reduces undifferentiated heavy lifting. Requires cost governance (FinOps) and strong IAM hygiene.
Private cloud: More platform ownership. You set standards, which can improve reliability across teams once established.
Typical use cases
Public cloud: Digital products with variable demand, data platforms, global web apps, partner APIs, rapid prototyping.
Private cloud: Regulated workloads, low-latency trading/industrial systems, fixed-throughput line-of-business apps, environments with strict residency or bespoke security controls.
Quick decision rubric
Uncertain demand, need speed? Start in public cloud.
Strict data control, predictable load? Favour private cloud.
Both apply? Go hybrid: run steady systems in private; burst and innovate in public.
Hybrid done right
Most mature setups blend the two: identity and policy unified, network stitched (VPN/Private Link), shared observability, and a consistent CI/CD path. Backups follow 3-2-1-1-0 across both estates, and DR plans assume either side can temporarily host the other’s crown jewels. Treat it as one logical infrastructure, not two silos.
The bottom line
There’s no universal winner. Public cloud maximises agility and reach; private cloud maximises control and predictability. Choose based on workload shape, compliance posture and team capability—then standardise tooling so your engineering experience is seamless whichever side your workloads live on.