Introduction
Recently, I came across a team that was breaking their perfectly healthy .NET application into nine smaller services because they heard the benefits of microservices at a tech conference. Six months later, they were paying for nine pipelines, two message brokers, and a tracing bill, and still shipping slower than they did with a big, single app.
This is the case with most of the other .NET teams in the market. They are rushing to microservices as if it were an offer that only a few can get. They just want to catch the trend and not pay attention to whether it is even worth it for them.
To be clear, I am not saying microservices in .NET are a bad choice. They can be the right one, just not for everyone.
So let me set the base first.
When a traditional monolith starts to slow down, teams usually reach for one of two answers: Either break the application into multiple microservices or keep it as one unit, but with clear internal boundaries separating its modules.
In .NET, with microservices, each domain, such as Identity or Billing, runs as its own service, with its own database and API, and they communicate over the network. On the other hand, a modular monolith means each domain, such as Identity or Billing, acts as a separate module with a clear boundary around it, and the application still runs and deploys as a single unit.
But, which of these approaches, between a modular monolith vs microservices in .NET, is better? Let us find out.
Top 7 Differences Between a Modular Monolith vs Microservices in .NET
Here's what modular monolith vs microservices actually means for a .NET team.
1. Deployment and release schedule
A modular monolith builds and deploys as one application. You run a single dotnet publish, and if a release breaks, you roll back that one app. Microservices let each service deploy on its own, but every service then needs its own build pipeline, its own version to track, and its own engineers on standby when it fails at night.
So, if the thing slowing your releases is testing and process, more and smaller services will not fix it.
2. In-process calls vs network latency
In a modular monolith, when one module needs something from another, it calls a method directly, usually through MediatR or a plain interface. That call runs in memory and comes back in microseconds.
Turn that module into a separate service, and the same call now travels over the network as HTTP or gRPC. The data has to be packed up and sent, the call can be slow, and it can fail on its own even when both sides are working fine, so you write code to retry it and to give up after a timeout.
Martin Fowler called this added cost the
"microservices premium."
You pay for it on every single call that used to be free.
3. Data ownership and distributed transactions
In a modular monolith, every module gets its own schema, but all the schemas sit inside one database. So when a single operation updates two modules at once, the database treats it as one transaction: either both updates go through, or neither does, and you never end up with half-finished data.
Split into services, and each module owns a separate database. That same operation now needs an outbox, a saga, and eventual-consistency handling that you have to write and test.
4. Debugging and failure isolation
When something breaks in a monolith, you read one error log that shows the whole path of the failure from start to finish.
In a distributed system, that same request may have passed through several services, each with its own logs, so you reassemble the path using correlation IDs and OpenTelemetry.
According to a 2025 CNCF survey, about 42% of organizations are consolidating services back into larger units, and debugging complexity sits near the top of their reasons.
5. How each model handles scaling
Microservices let you scale just the part of your .NET app that needs it. If image processing is the slowest piece of your system, you run more copies of that one service and leave everything else alone.
A modular monolith scales differently: you run more copies of the whole application, not individual parts of it.
For most .NET systems, that is fine, because the whole app is cheap to run and only one or two areas ever come under heavy load. The targeted scaling that microservices offer only pays off when you actually have parts with very different load levels, which many teams expect to need and never do.
6. Team size and code ownership
Microservices work best for a .NET app when each service belongs to a separate team that builds and releases it on its own schedule. That setup starts to make sense once the engineering group gets large, often past roughly 50 developers, because at that point teams genuinely get in each other's way inside a single codebase.
A modular monolith fits the more common case: a smaller group working in one codebase, where clear module boundaries give each person their own area to own without the overhead of separate services. The harder part is drawing those module boundaries well within one codebase, which takes experience.
If you do not have the expertise or resources to follow through on your choice, it helps to hire .NET developers who have done it before.
7. Operational overhead and headcount
Every microservice is one more thing to host, secure, and monitor. A CTO pays for that twice: the cloud bill, then the platform engineers hired to keep all of it healthy. Service mesh, the tooling meant to tame this, is losing adoption as teams decide it costs more than it returns.
Step back from the list and the modular monolith vs microservices decision keeps landing on one thing: scale you can prove, not scale you hope for.
Conclusion
When making a choice between modular monolith vs microservices in .NET, you do not have to just choose one side and stick with it forever.
If you build the modular monolith well, with each module behind a clear boundary and its own schema, you can move a single module into its own service later. .NET Aspire helps with this. It manages how your modules and services find and call each other, so when you move one out, the rest of the app keeps calling it the same way, and you do not rewrite connection code.
So start with the modular monolith. Move a module to its own service when you have a clear reason, not before.
If you want a second opinion on what you should choose, you can take the help of .NET consulting services provider. They will assess your current application and help make the right choice and implement it successfully.
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