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May 15, 2024
4 min read

Horizontal vs Vertical Scaling: Why Its Like Managing Teams

Scale up or scale out? Why adding servers is like hiring people - and why both approaches have similar challenges.

Horizontal vs Vertical Scaling: Why Its Like Managing Teams

Think about growing your engineering team. You have two options:

  1. Make your best developer even better (vertical)
  2. Hire more developers (horizontal)

Same with servers. You can:

  1. Make one server stronger (vertical scaling)
  2. Add more servers (horizontal scaling)

Let’s see why these are surprisingly similar.

Vertical Scaling (“Scale Up”)

With Servers:

  • Bigger CPU
  • More RAM
  • Faster disks
  • More cores

With People:

  • More training
  • Better tools
  • More responsibilities
  • Higher expertise

Pros:

  • Simple to manage (one unit)
  • No coordination overhead
  • Predictable performance
  • Easy deployment

Cons:

  • Physical limits
  • Single point of failure
  • Expensive at high end
  • Downtime during upgrades

Horizontal Scaling (“Scale Out”)

With Servers:

  • More machines
  • Load balancers
  • Distributed data
  • Service discovery

With People:

  • More team members
  • Team leads/coordinators
  • Knowledge sharing
  • Communication tools

Pros:

  • Nearly unlimited scaling
  • Fault tolerance
  • Cost effective
  • Rolling updates

Cons:

  • Complex coordination
  • Data consistency issues
  • Network overhead
  • Management overhead

The Communication Problem

Vertical (1 Unit):
┌──────────┐
│ DO THING │
└──────────┘

Horizontal (3 Units):
┌────────┐  ┌────────┐  ┌────────┐
│DO PART │──│DO PART │──│DO PART │
└────────┘  └────────┘  └────────┘
    │           │           │
    └───────────┴───────────┘
     Communication Overhead

Just like teams need meetings, servers need network calls.

Team Issues:

  • Timezone differences
  • Misunderstandings
  • Sick days
  • Knowledge silos

Server Issues:

  • Network latency
  • Message failures
  • Server downtime
  • Data sync delays

Common Patterns

Load Distribution

Teams:

Before:
PM → Super Developer (overwhelmed)

After:
          ┌→ Developer 1
PM → Lead ├→ Developer 2
          └→ Developer 3

Servers:

Before:
Users → Big Server (maxed out)

After:
           ┌→ Server 1
Users → LB ├→ Server 2
           └→ Server 3

Backup Plans

Teams:

  • Cross-training
  • Documentation
  • Shared knowledge
  • Backup leads

Servers:

  • Failover systems
  • Redundant data
  • Health checks
  • Backup instances

Real Examples

Vertical Scaling:

  • High-frequency trading (one super-fast machine)
  • Complex calculations (big GPU server)
  • In-memory databases (huge RAM server)

Horizontal Scaling:

  • Web services (multiple app servers)
  • Big data processing (distributed computing)
  • Global services (servers worldwide)

When to Choose What

Go Vertical When:

  • Simple workloads
  • Need predictable performance
  • Can’t split the work
  • Budget isn’t main concern

Go Horizontal When:

  • Heavy workloads
  • Need fault tolerance
  • Work is parallelizable
  • Cost-sensitive

Hybrid Approach

Most real systems use both:

Users → Load Balancer →┌→ Strong Server 1
                       ├→ Strong Server 2
                       └→ Strong Server 3

Just like most companies have:

  • Some senior developers (vertical)
  • Multiple teams (horizontal)

Common Issues

1. Communication Overhead

Teams:

2 people = 1 communication channel
3 people = 3 channels
4 people = 6 channels
5 people = 10 channels

Servers:

2 servers = 1 network path
3 servers = 3 paths
4 servers = 6 paths
5 servers = 10 paths

2. Consistency

Teams:

  • Different understandings
  • Out-of-sync information
  • Conflicting decisions

Servers:

  • Data inconsistency
  • Race conditions
  • Conflicting updates

3. Cost vs Benefit

Both follow diminishing returns:

  • One great developer ≠ 10 average developers
  • One powerful server ≠ 10 small servers

Bottom Line

Start vertical (simpler), add horizontal (more resilient) when needed.

Signs you need horizontal scaling:

  • Single unit maxed out
  • Need fault tolerance
  • Different geographic regions
  • Cost of vertical too high

Remember: The complexity jump from 1 to 2 units is bigger than 2 to 10. Plan for it.