Skip to main content

System Design for Platform Engineers

System design interviews for platform engineering roles focus on building reliable, scalable, and maintainable infrastructure. Unlike product-focused system design, you'll need to demonstrate deep understanding of distributed systems, infrastructure components, and operational excellence.

Platform Engineering System Design Focus Areas​

What Makes Platform Engineering Design Different​

  1. Infrastructure First: Design systems that other teams build upon
  2. Operational Excellence: Consider monitoring, debugging, and maintenance from day one
  3. Cost Optimization: Balance performance with resource efficiency
  4. Multi-tenancy: Design for multiple teams and applications
  5. Security and Compliance: Build security into the platform layer

System Design Interview Framework​

1. Requirements Gathering (5-10 minutes)​

Functional Requirements:

  • What services need to be supported?
  • What are the SLAs/SLOs?
  • What scale are we designing for?
  • What are the integration points?

Non-Functional Requirements:

  • Availability targets (99.9%, 99.99%?)
  • Latency requirements
  • Throughput expectations
  • Security and compliance needs
  • Cost constraints

Example Questions to Ask:

  • "What's our target availability?"
  • "What's the expected request rate?"
  • "What regions do we need to support?"
  • "What's our budget constraint?"
  • "What compliance requirements exist?"

2. Capacity Estimation (5 minutes)​

Calculate:

  • Requests per second (RPS)
  • Storage requirements
  • Bandwidth needs
  • Server/container count
  • Cost estimates

Example Calculation:

Daily Active Users: 10M
Requests per user: 100/day
Total requests: 1B/day = 11,574 RPS
Peak traffic: 3x average = 34,722 RPS
With 20% headroom: 41,666 RPS needed

3. High-Level Design (10-15 minutes)​

Start with major components:

  • Load balancers
  • API gateways
  • Service mesh
  • Data stores
  • Message queues
  • Caching layers
  • Monitoring stack

4. Detailed Design (15-20 minutes)​

Deep dive into:

  • Data flow
  • API design
  • Database schema
  • Caching strategy
  • Security measures
  • Monitoring and alerting

5. Scale and Optimize (10 minutes)​

Discuss:

  • Bottlenecks
  • Scaling strategies
  • Performance optimization
  • Cost optimization
  • Disaster recovery

Common Platform Engineering System Design Questions​

1. Design a CI/CD Platform​

Requirements:

  • Support 1000+ developers
  • Multiple programming languages
  • 10,000 builds/day
  • Artifact storage
  • Security scanning

Key Components:

┌─────────────┐     ┌──────────────┐     ┌──────────────┐
│   Git Repo  │────▶│  Webhook/API │────▶│ Build Queue  │
└─────────────┘     └──────────────┘     └──────────────┘
                                                  │
                                                  ▼
┌─────────────┐     ┌──────────────┐     ┌──────────────┐
│   Builders  │◀────│   Scheduler  │     │ Orchestrator │
└─────────────┘     └──────────────┘     └──────────────┘
        │
        ▼
┌─────────────┐     ┌──────────────┐     ┌──────────────┐
│  Artifacts  │     │Test Results  │     │  Deployment  │
└─────────────┘     └──────────────┘     └──────────────┘

Design Considerations:

  • Build isolation (containers/VMs)
  • Queue management (Kafka/RabbitMQ)
  • Artifact storage (S3/Artifactory)
  • Secret management
  • Build caching
  • Monitoring and metrics

Resources:

2. Design a Container Orchestration Platform​

Requirements:

  • Manage 10,000+ containers
  • Multi-region deployment
  • Auto-scaling
  • Service discovery
  • Zero-downtime deployments

Key Components:

┌─────────────────┐
│   Control Plane │
├─────────────────┤
│ • API Server    │
│ • Scheduler     │
│ • Controller    │
│ • etcd          │
└────────┬────────┘
         │
    ┌────┴────┐
    ▼         ▼
┌────────┐ ┌────────┐
│ Node 1 │ │ Node 2 │
├────────┤ ├────────┤
│ Kubelet│ │ Kubelet│
│ Proxy  │ │ Proxy  │
│Runtime │ │Runtime │
└────────┘ └────────┘

Design Considerations:

  • Control plane high availability
  • Network policies and CNI
  • Storage orchestration
  • Resource allocation
  • Security policies
  • Multi-tenancy

Resources:

3. Design a Monitoring and Observability Platform​

Requirements:

  • 1M metrics/second
  • 100TB logs/day
  • Distributed tracing
  • 99.9% availability
  • 30-day retention

Key Components:

┌─────────────┐     ┌──────────────┐     ┌──────────────┐
│   Agents    │────▶│  Collectors  │────▶│   Storage    │
└─────────────┘     └──────────────┘     └──────────────┘
                            │                      │
                            ▼                      ▼
                    ┌──────────────┐      ┌──────────────┐
                    │   Querying   │◀─────│ Aggregation  │
                    └──────────────┘      └──────────────┘
                            │
                            ▼
                    ┌──────────────┐
                    │Visualization │
                    └──────────────┘

Design Considerations:

  • Time-series database selection
  • Data retention policies
  • Sampling strategies
  • Query performance
  • Alert management
  • Data compression

Resources:

4. Design a Service Mesh​

Requirements:

  • Handle 100K RPS
  • mTLS between services
  • Traffic management
  • Circuit breaking
  • Observability

Key Components:

┌────────────────┐
│  Control Plane │
├────────────────┤
│ • Config Mgmt  │
│ • Cert Mgmt    │
│ • Policy Engine│
└───────┬────────┘
        │
┌───────▼────────┐
│   Data Plane   │
├────────────────┤
│ Sidecar Proxies│
│ (Envoy)        │
└────────────────┘

Resources:

5. Design a Multi-Region Database Platform​

Requirements:

  • Global distribution
  • Strong consistency options
  • 99.99% availability
  • Automatic failover
  • Compliance with data residency

Key Components:

┌─────────────────────────────────────┐
│         Global Coordinator          │
└─────────────┬───────────────────────┘
              │
    ┌─────────┴─────────┬─────────────┐
    ▼                   ▼             ▼
┌─────────┐      ┌─────────┐   ┌─────────┐
│Region 1 │      │Region 2 │   │Region 3 │
├─────────┤      ├─────────┤   ├─────────┤
│ Primary │◀────▶│ Replica │◀─▶│ Replica │
└─────────┘      └─────────┘   └─────────┘

Resources:

Platform-Specific Design Patterns​

1. Reliability Patterns​

Circuit Breaker

class CircuitBreaker:
    def __init__(self, failure_threshold=5, recovery_timeout=60):
        self.failure_threshold = failure_threshold
        self.recovery_timeout = recovery_timeout
        self.failure_count = 0
        self.last_failure_time = None
        self.state = 'CLOSED'

Bulkhead Pattern

  • Isolate resources to prevent cascade failures
  • Use connection pools with limits
  • Implement thread pool isolation

Resources:

2. Scalability Patterns​

Horizontal Scaling

  • Stateless services
  • Shared-nothing architecture
  • Database sharding

Caching Strategies

  • Cache-aside
  • Write-through
  • Write-behind
  • Refresh-ahead

Resources:

3. Security Patterns​

Zero Trust Architecture

  • Verify explicitly
  • Least privilege access
  • Assume breach

Secret Management

  • Centralized secret store
  • Dynamic secret generation
  • Secret rotation

Resources:

System Design Resources​

Books​

Online Courses​

Practice Resources​

Mock Interviews​

Common Pitfalls to Avoid​

  1. Over-engineering: Don't design for 1B users when asked for 1M
  2. Ignoring constraints: Always consider cost, team size, timeline
  3. Missing monitoring: Every design needs observability
  4. Forgetting security: Security should be built-in, not bolted-on
  5. Neglecting operations: Consider how the system will be maintained

Tips for Success​

  1. Think out loud: Verbalize your thought process
  2. Start simple: Begin with a basic design and iterate
  3. Draw diagrams: Visual representations help communicate ideas
  4. Consider trade-offs: Every decision has pros and cons
  5. Ask questions: Clarify requirements and constraints
  6. Know your numbers: Memorize common latency and capacity figures

Latency Numbers Every Platform Engineer Should Know​

L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns
Compress 1K bytes with Zippy             3,000   ns
Send 1K bytes over 1 Gbps network       10,000   ns
Read 4K randomly from SSD               150,000   ns
Read 1 MB sequentially from memory      250,000   ns
Round trip within same datacenter       500,000   ns
Read 1 MB sequentially from SSD       1,000,000   ns
Disk seek                            10,000,000   ns
Read 1 MB sequentially from disk     20,000,000   ns
Send packet CA->Netherlands->CA     150,000,000   ns

Remember: System design for platform engineering is about building the foundation that enables other teams to succeed. Focus on reliability, scalability, and operational excellence in every design decision.