Understanding Monorepos

Understanding
monorepos
@PhilipJFulcher
@bencabanes nx.dev • nrwl.io powered by

Hi 👋 
I’m Benjamin Cabanes
🇨🇦 · 🐬
Javascript Architect @ Nrwl 
Nx Core Team
@bencabanes
@PhilipJFulcher
@bencabanes powered by

Hi 👋 
I’m Philip Fulcher
🇺🇸 · 🐬
Nx Core Team Member
@philipjfulcher
@PhilipJFulcher

Why do companies
use monorepos?
@PhilipJFulcher

SHORT
ANSWER?
@PhilipJFulcher

Why do companies use
monorepos?
• Manage complexity
• Organization-wide best
practices
• Maximizing shared code
• Consistency & predictability in
code
• Discoverability and
communication
• Foster collaboration
@PhilipJFulcher

LONG
ANSWER?
@PhilipJFulcher

Let’s talk about
monorepos…
@PhilipJFulcher

What is a
monorepo?
@PhilipJFulcher

A monorepo is a single repository
containing multiple distinct projects,
with well-de
fi
ned relationships.
@PhilipJFulcher

@PhilipJFulcher

You projects in the
same place
• High level view of projects
• Allows collaboration
• Removes assumptions
• Project discoverability
• Code reuse
• Architecture discoverability
@PhilipJFulcher

✋ Monolith ≠ Monorepo ✋
@PhilipJFulcher

Monolith & Monorepo are different concepts 
A monorepo is about code organization
A monolith is about code linking and particular type of deployment
@PhilipJFulcher

Well-de
fi
ned relationships are
used by tooling to provide
automation & assistance
@PhilipJFulcher

00
V1
Date
Presentation Subtitle
Presentation Title
@PhilipJFulcher

Cross-project changes
Architecture awareness
Relationships
are key
Performance with
smart commands
Project graph
Projects discoverability & always
up to date visual representation
Test/build only affected code
Identify relations & contracts
Smart code generation
Adds a smart layer to
project relationships
@PhilipJFulcher

Smarter tooling
Better DX
Collaboration & Productivity increase
@PhilipJFulcher

Wait. So what’s wrong
with my polyrepo setup? 🤔
@PhilipJFulcher

Well, nothing is really
*wrong*. It’s just…
@PhilipJFulcher

Polyrepos have a high
cost of maintenance.
@PhilipJFulcher

Polyrepos are dif
fi
cult
to scale.
@PhilipJFulcher

A common situation
with polyrepos
Let’s share
some code!
@PhilipJFulcher

Sharing code with
polyrepos
4/ Write the shareable code
5/ CI & CD checks
6/ Deploy & publish to registry
1/ Create repository, setting
permissions, team management
2/ Setup CI & CD (waiting from
IT team)
3/ Setup tooling for build, serve,
lint …
@PhilipJFulcher

- Write the shared code
Sharing code with
monorepos
- Test consuming projects
directly from where you are.
All changes are done in a single PR
Consumers are all tested (high con
fi
dence) 
No externals, faster merge and release
- Use existing code, tooling
@PhilipJFulcher

Sharing code with
polyrepos
- depends on published artefacts
- Changes, PRs, Code reviews, CI/
CD runs times “n” for each repo
- Takes time to complete and
start using the shared code.
@PhilipJFulcher

Sharing code with
polyrepos
A: v1.0
B: v1.0 C: v1.0
D: v1.0
A: v1.0
B: v1.0 C: v1.1
B: v1.0 C: v1.1
A: v1.0
B: v1.0 C: v1.1
D: v1.0 D: v1.1
😨
😎 😱
💎The Diam
on
d Dependency Problem 💎
@PhilipJFulcher

Polyrepos creates silos &
makes collaboration
harder.
@PhilipJFulcher

It is easy to do the wrong
things when working in
silos.
@PhilipJFulcher

Polyrepos and monoliths
are pretty common.
@PhilipJFulcher

The industry has moved to the
polyrepo to get team autonomy.
@PhilipJFulcher

Autonomy by isolation
harms collaboration.
@PhilipJFulcher

What about
monorepos then?
@PhilipJFulcher

Monorepos do
relationships analysis
@PhilipJFulcher

One version of everything
03
Atomic commit across projects
02
No overhead to create new projects
01
Developer mobility
05
Consistent tooling
04
Monorepos
bene
fi
ts
@PhilipJFulcher

I can’t use a monorepo.
I do micro frontends. 😏
@PhilipJFulcher

Again, a common
misconception.
@PhilipJFulcher

No more assumptions,
all the code is here,
easier to debug with monorepos
@PhilipJFulcher

A monorepo makes micro-
frontends easier & manageable
@PhilipJFulcher

If everyone has access to
everything. Then it’s
unmanageable. Right? 😱
@PhilipJFulcher

Polyrepo
code ownership?
No high level overview
No structure
Everyone can depend on everything
Permissions per repository
@PhilipJFulcher

Monorepo 
code ownership
High level overview
Visible structure & enforced by tooling
Clear hierarchy and dependencies
Granular access:
- constraints per import
- constraints per folder
- constraints per project
- custom constraints with tooling
@PhilipJFulcher

Relationships are key to
monorepos
@PhilipJFulcher

00
V1
Date
Presentation Subtitle
Presentation Title

Why is Nx the right
tool for your
Monorepo?
@PhilipJFulcher

Not just code
colocation
@PhilipJFulcher

Projects
@PhilipJFulcher

Knowledge Base 
feat-knowledge-base
Live Chat 
feat-live-chat
Support Tickets
feat-support-tickets
New Ticket
feat-new-ticket
Libraries
Customer Service App
App
@PhilipJFulcher

- Name
- Path Alias
- Well-de
fi
ned API
Each project
has
@PhilipJFulcher

cart-ui-components
@PhilipJFulcher

@myorg/cart/ui-components
@PhilipJFulcher

Well-De
fi
ned
Relationships
@PhilipJFulcher

Tags
@PhilipJFulcher

Module
Boundaries
@PhilipJFulcher

Microfrontends 😎
@PhilipJFulcher

Superpowered
Micro Frontends with
Monorepos
@PhilipJFulcher

Speeding up day-to-
day development
@PhilipJFulcher

Targets
@PhilipJFulcher

Testing
@PhilipJFulcher

Affected Commands
- affected:test
- affected:build
- affected:e2e
@PhilipJFulcher

Never run the same target
twice.
@PhilipJFulcher

Nx Cloud
@PhilipJFulcher

Into the (Nx) Clouds
@PhilipJFulcher

Atomic Changes
@PhilipJFulcher

Project
Graph
@PhilipJFulcher

Experimentation
@PhilipJFulcher

Generators
@PhilipJFulcher

Workspace Generators
@PhilipJFulcher

Keys take away on
monorepos
@PhilipJFulcher

Monorepos are not just about
code colocation
@PhilipJFulcher

Well-de
fi
ned relationships between
isolated units of code are essential
@PhilipJFulcher

Good tools & automation are needed for
a monorepo to scale with the
organization
@PhilipJFulcher

nx.dev
monorepo.tools
@PhilipJFulcher

Understanding Monorepos

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