The Case Against a Mono-Deployment Model for Software Projects

Executive Summary

Consider a development team that maintains a large monolithic repository with several projects. One service, Jobs.Api, functions almost entirely autonomously except for a single stored-procedure call to the MainWeb database. Adopting a mono-deployment model—where every project ships together—introduces elevated failure risk, lengthier release cycles, and scaling inefficiencies. A modular deployment strategy, ideally by separating Jobs.Api into its own repository, improves reliability, speed, and clarity of ownership while leveraging AWS CodeDeploy’s strengths.

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Introduction

In this example scenario, a single repository contains console utilities, web applications, and an EF-Core migration project under the MainWeb banner. Jobs.Api relies on the rest of the codebase only through one stored procedure, yet deploying the entire codebase together can allow unrelated changes to disrupt otherwise stable services. The following sections outline the drawbacks of mono-deployment and present modular alternatives suited to a small, distributed team using AWS CodeDeploy.

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Problems with the Mono-Deployment Model

Issue	Explanation
Higher failure risk	Bundling unrelated changes allows a harmless update (e.g., a console tool) to break Jobs.Api. Martin Fowler refers to this as “accidental coupling,” which expands the blast radius of any defect.
Slower release cycles	Even trivial fixes force full builds and tests across every project, delaying delivery for an otherwise independent service.
Inefficient scaling	Distinct projects have different resource profiles; one-size-fits-all infrastructure wastes capacity and money.
Coordination friction	In a monorepo without formal code reviews, ownership boundaries blur, leading to merge conflicts and late-night emergencies across time zones.

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Benefits of Modular Deployment

• Isolated releases – Updating Jobs.Api runs only its pipeline, making rollbacks surgical.

• Faster CI/CD – Smaller codebase equals shorter test and build times.

• Right-sized infrastructure – Each service scales independently via AWS CodeDeploy deployment groups.

• Clear ownership – Separate repositories or bounded contexts make responsibility unmistakable, reducing errors in teams without mandatory reviews.

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Industry Guidance

• Monorepo vs. Polyrepo – ThoughtWorks, GitHub, and Martin Fowler note that tightly coupled monorepos can slow delivery, whereas polyrepos simplify independent deployments.

• Selective builds – Tools such as Nx can restrict builds to the code that changed, but extracting an autonomous service is simpler and less brittle.

• AWS CodeDeploy – Deployment groups, blue/green, and canary strategies are geared toward modular rollouts—not all-at-once releases.

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Practical Recommendations

1. Move Jobs.Api to its own repository.

   • Independent CI/CD pipeline using AWS CodeBuild ➜ S3 ➜ CodeDeploy.

   • Blue/green deployments limit downtime and risk.

2. Maintain a separate pipeline for MainWeb.

   • Database migrations run first; web apps follow.

3. Sequence database changes.

   • CodePipeline stages enforce “migrations → API” order so stored-procedure compatibility is preserved.

4. Fallback: selective deployment inside a monorepo.

   • Configure Nx (or a comparable tool) to build only the changed project and provide a project-specific AppSpec file for CodeDeploy.

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Addressing Typical Objections

Concern	Response
“Multiple repos increase overhead.”	Modern tooling (GitHub Actions, Dependabot, branch protection) automates much of the extra work.
“Cross-repo database dependency is fragile.”	Pipeline stages can enforce migration order; stored procedures can be versioned.
“The team is small; one repo feels simpler.”	Independent deployments actually reduce firefighting effort—crucial when headcount and review bandwidth are limited.

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Conclusion

Mono-deployment amplifies risk, slows iteration, and impedes efficient scaling. Splitting Jobs.Api into its own repository—or, at minimum, deploying it independently—follows proven best practices, leverages AWS CodeDeploy’s capabilities, and enables faster, safer delivery with unmistakable ownership, benefiting any small, distributed team.

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Key References

• Martin Fowler – Monorepo vs. Polyrepo

• GitHub Docs – Repository Best Practices

• AWS CodeDeploy – Deployment Groups

• CircleCI – Monorepo Benefits & Challenges

• Semaphore – Smart Build Systems for Monorepos

• ThoughtWorks Technology Radar – Modular vs. Monolithic Architecture

• StackOverflow – Deploying Subdirectories with AWS CodeDeploy

• Nx .NET – Monorepo Management for .NET