Firmitas ¡ Utilitas ¡ Venustas

Firmitas: Strength
Structural integrity
Durability
Reliability over time

Utilitas: Use
Fitness for purpose
Human needs
Function without friction

Venustas: Beauty
Harmony
Proportion
Meaning and dignity

Skill: Craft + Technique

Learning by doing, where practice, repetition, and reflection turn raw talent into reliable technique. As Vitruvius reminds us:
“For neither talent without instruction nor instruction without talent can produce the perfect craftsman.”

Before you design systems, you must understand the world they live in. Architects often feel like generalists among specialists. The architect is not the best engineer, artist, or builder, but the one who knows enough of each to arbitrate wisely.

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Top IT APIs Every Startup Should Know

A curated set of APIs used in real-world startup systems.

Cloud & Infrastructure

AWS APIs

Compute, storage, IAM

Cloud & Infrastructure

Google Cloud APIs

Serverless cloud services

Cloud & Infrastructure

Cloudflare API

DNS, CDN, security

Developer & DevOps

GitHub REST API

Repositories and CI signals

Developer & DevOps

GitLab API

CI/CD pipelines

Developer & DevOps

Kubernetes API

Cluster automation

Auth & Security

Auth0 API

Authentication workflows

Auth & Security

Okta API

SSO and enterprise IAM

Auth & Security

VirusTotal API

Threat analysis

Monitoring & Ops

Prometheus API

Metrics and monitoring

Monitoring & Ops

Grafana API

Dashboards and observability

Monitoring & Ops

PagerDuty API

Incident management

Payments & Data

Stripe API

Payments infrastructure

Payments & Data

Exchange Rates API

Currency conversion

Payments & Data

IPinfo API

IP intelligence

Testing & Automation

Postman API

API testing platform

Testing & Automation

k6 API

Load testing

Testing & Automation

Lighthouse API

Performance audits

Testing & Automation

Ansible API

Infrastructure automation

Testing & Automation

ServiceNow API

IT service workflows

Top 5 in-demand IT exams (live Google Trends)

🍰 ArxCafe

Welcome to ArxCafe a calm, secure place to sit your exams online.

Why Learn with Us?
BEGINNER
  1. Client – Server
  2. HTTP vs HTTPS
  3. Request / Response
  4. HTTP Methods (GET, POST, PUT, DELETE)
  5. HTTP Status Codes
  6. Headers and Body
  7. Stateless Communication
  8. Domain Name System (DNS)
  9. DNS Resolution
  10. IP Address (Public vs Private)
  11. Ports (80, 443)
  12. TCP vs UDP
INTERMEDIATE
  1. TLS Handshake
  2. Digital Certificates
  3. Public Key vs Private Key
  4. Encryption in Transit
  5. Authentication vs Authorization
  6. Tokens (Session, JWT, API Key)
  7. Application Architecture
  8. Monolith
  9. Modular Monolith
  10. Microservices
  11. API Gateway
  12. Synchronous vs Asynchronous Communication
  13. REST APIs
  14. JSON
  15. API Versioning
  16. Pagination
  17. Rate Limiting
  18. Webhooks
  19. Databases (Relational)
  20. Databases (NoSQL)
  21. Read vs Write Operations
  22. Indexing
  23. Backups
  24. Caching
ADVANCED
  1. Vertical Scaling
  2. Horizontal Scaling
  3. Load Balancer
  4. Content Delivery Network (CDN)
  5. Latency
  6. Throughput
  7. Health Checks
  8. Failover
  9. Replication
  10. High Availability
  11. Disaster Recovery
  12. Logging
  13. Metrics
  14. Monitoring
  15. Alerts
  16. Distributed Tracing
  17. CI/CD Pipeline
  18. Build – Test – Deploy
  19. Environments (Dev / Test / Prod)
  20. Secrets Management
  21. Rollback
  22. Virtual Machines
  23. Containers
  24. Docker
  25. Managed Services
  26. Regions and Availability Zones
📘 Google Professional Machine Learning Engineer
Layered Concepts
Purpose

A concept-first, layered learning framework that explains Machine Learning systems from first principles to production-scale deployment, aligned with Google Cloud Professional Machine Learning Engineer exam objectives.

Design Goals
  • Explain concepts from fundamentals to advanced systems
  • Assume zero prior Machine Learning knowledge
  • Follow a strict layer-by-layer dependency model
  • Make failure modes explicit
  • Serve as long-term reference material (not just exam prep)
  • Align with Google Cloud ML engineering expectations
Layered Structure
Click a layer to expand.
Layer 0 — Mathematical & Statistical Foundations (Bedrock)
What it is: Math and probability behind learning from data
Why it exists: Models are optimized mathematical functions
If skipped: ML becomes a black box with no intuition
Layer 1 — Data & Programming Foundations
What it is: Data handling, cleaning, and exploration
Why it exists: Models depend entirely on data quality
If skipped: Garbage-in, garbage-out failures
Layer 2 — Machine Learning Fundamentals
What it is: Core ML algorithms and evaluation
Why it exists: Different problems require different learning assumptions
If skipped: Wrong model choices and poor metrics
Layer 3 — Feature Engineering & Representation
What it is: Transforming raw data into learnable signals
Why it exists: Models only learn from exposed features
If skipped: Underperforming models regardless of algorithm
Layer 4 — Deep Learning & Representation Learning
What it is: Neural networks and automatic feature learning
Why it exists: Manual features don’t scale for complex data
If skipped: Misuse or avoidance of deep learning
Layer 5 — Data Pipelines & Training Systems
What it is: Scalable, reproducible data and training workflows
Why it exists: ML systems depend on reliable data flow
If skipped: Non-reproducible and fragile systems
Layer 6 — ML on Google Cloud (Infrastructure)
What it is: Cloud-native ML training, serving, and scaling
Why it exists: Real ML must operate at production scale
If skipped: Models cannot be reliably deployed
Layer 7 — MLOps & Model Lifecycle
What it is: Monitoring, versioning, and retraining models
Why it exists: Models degrade over time
If skipped: Silent performance decay
Layer 8 — Responsible AI, Security & Governance
What it is: Fairness, explainability, privacy, compliance
Why it exists: ML systems affect real users
If skipped: Ethical, legal, and reputational risk
Layer 9 — End-to-End System Design (Integration)
What it is: Full ML system design under constraints
Why it exists: This is how ML works in the real world
If skipped: Inability to design or justify ML systems

Architecture Evolution

Startup
Infrastructure
  • Single cloud
  • Few regions
  • Managed services
  • Cost-first
Network Architecture
  • Single VPC / flat network
  • Public ingress, private services
  • Basic firewall rules
System Architecture
  • Monolith or modular monolith
  • Synchronous request–response model (async implementation)
Software Architecture
  • MVC or layered
  • Minimal abstraction
Data Architecture
  • Single database
  • Simple schema
  • Basic backups
Security
  • Basic auth & HTTPS
  • Env secrets
  • OWASP basics
API Architecture
  • REST
  • Few versions
  • Minimal docs
Scalability
  • Vertical scaling
  • CDN
  • Basic caching
Performance
  • Fast enough
  • Simple caching
  • Basic monitoring
Reliability
  • Best-effort availability
  • Manual recovery
Observability
  • Logs and basic metrics
DevOps & Delivery
  • Simple CI/CD
  • Manual approvals
Testing
  • Unit tests
  • Limited integration tests
Governance & Process
  • Informal decisions
  • Minimal docs
Cost Management
  • Minimize spend
  • Shared resources
Enterprise
Infrastructure
  • Multi-region
  • Hybrid / multi-cloud
  • Strict DR
  • IaC everywhere
Network Architecture
  • Segmented networks
  • Private connectivity
  • Zero Trust networking
  • Controlled ingress & egress
System Architecture
  • Microservices
  • Event-driven, async messaging
Software Architecture
  • Clean/Hexagonal
  • DDD, strict boundaries
Data Architecture
  • Multiple databases
  • Replication & sharding
  • Governance
Security
  • Central IAM
  • SSO / MFA
  • RBAC/ABAC & compliance
API Architecture
  • REST / GraphQL / gRPC
  • Contract-first
  • Versioning policies
Scalability
  • Horizontal scaling
  • Queues
  • Multi-region active-active
Performance
  • Latency budgets & SLAs
  • Continuous load testing
  • Performance monitoring
Reliability
  • High availability
  • Automated failover
  • Chaos testing
Observability
  • Centralized logging
  • Tracing
  • Dashboards
  • On-call
DevOps & Delivery
  • Multi-stage pipelines
  • Canary / blue-green deploys
Testing
  • Full test pyramid
  • Security & performance testing
Governance & Process
  • Architecture reviews
  • ADRs
  • Formal standards
Cost Management
  • Cost allocation
  • Budgets
  • FinOps practices