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Monday, 29 December 2025
Microservices have become the default "serious system" architecture.
If you want to sound mature, you talk about service meshes, event buses, distributed tracing, and "independent deployability". If you want to look enterprise-ready, you draw boxes until the diagram looks like a bowl of spaghetti someone threw at a whiteboard.
But here's the corrective most juniors aren't being given:
Microservices are not an application architecture upgrade. They are an organisational scaling strategy.
If you don't already have the organisational pain they solve, adopting them early doesn't make you future-proof. It makes you present-broken.
This isn't a theoretical argument. It's an engineering trade-off, and like all trade-offs, it only makes sense when you understand the tax you're paying and what you're getting in return.
I've been as guilty as anyone of "doing microservices" without fully internalising the organisational overhead they entail. It's easy to get caught up in the vocabulary and forget that the real challenge is managing complexity across teams and systems.
In the end it comes down to the oldest pattern in software engineering: KISS - keep it simple, stupid.
Microservices are sold as a default architecture because the narrative is seductive:
This framing is backwards.
Microservices aren't primarily about code structure. They're about who can change what, without talking to whom, and how often.
If you don't have:
…then you're not solving an organisational problem. You're buying one.
Architecture is ultimately about enabling people, not moving boxes around.
You've seen this diagram.
This is not an "example architecture to copy". It's a warning label.
Courses often teach microservices as diagrams because diagrams are easier than teaching operational responsibility.
The important reframing is this: that diagram is not a target state. It's a cost surface.
Every box is a commitment:
The arrows look impressive. They also hide reality.
Because each arrow is:
If an architecture requires this on day one, you are not building a product. You are building a platform.
Like all architectural decisions, microservices come with a complexity tax (see Playing with Code: complexity tax. The difference is that this tax compounds across every service boundary, every deployment, and every failure mode.
The costs are rarely explicit. They're usually disguised as "best practice".
Each service wants:
If a team can't do this comfortably, it doesn't have microservices. It has a distributed monolith with extra steps.
In a monolith, a call is a function call.
In microservices, a "call" is a negotiated truce between:
Failure modes multiply:
You don't debug bugs anymore. You debug system states.
Here's a cost that's almost never discussed in microservices advocacy: serialization and deserialization (SerDe) overhead.
Every service boundary means:
// Monolith: direct object reference
var user = _userService.GetUser(userId); // < 1μs
var tier = user.Tier; // Memory access
// Microservices: serialize → network → deserialize
var json = JsonSerializer.Serialize(user); // ~50μs for a complex object
var bytes = Encoding.UTF8.GetBytes(json); // ~10μs
// ... send over network ...
var responseJson = await response.Content.ReadAsStringAsync(); // ~20μs
var user = JsonSerializer.Deserialize<User>(responseJson); // ~70μs
var tier = user.Tier; // Finally
Per call, that's ~150μs of pure CPU overhead before the network even gets involved.
Now multiply that across a call chain:
In a 5-service chain, you're spending ~1.5ms just on SerDe - and that's optimistic JSON serialization. If you're using XML, Protocol Buffers with reflection, or inefficient serializers, multiply that by 2-10x.
Yes, you can reduce this with techniques like JSON source generation in .NET:
[JsonSerializable(typeof(User))]
internal partial class UserJsonContext : JsonSerializerContext { }
// ~30-40% faster than reflection-based serialization
var json = JsonSerializer.Serialize(user, UserJsonContext.Default.User);
But you're still doing serialization. You've just made the tax slightly cheaper. In a monolith, the tax is zero.
I once profiled an address search system with this architecture (all in Kubernetes containers):
ASP.NET API → Go Service (fan-out) → ASP.NET Search Service → Elasticsearch
The Go service handled fan-out to multiple data sources and aggregated results. Each request meant multiple serialization hops across container boundaries.
The breakdown for a typical address search:
For a 3-backend fan-out:
We were spending nearly as much time on SerDe as we were on actual searching.
The cost wasn't the Go service itself - fan-out made sense for the use case. The cost was the service boundaries. Every container border meant serialize → network → deserialize.
In a monolith doing the same fan-out logic:
This cost:
In a monolith, this cost is zero. The object is already in memory.
Here's a common sales pitch: "Microservices improve performance."
This is backwards.
Microservices are slower for the same compute resources. Let's be precise about what we mean:
Throughput (requests per second per CPU core):
Scalability (ability to handle more total requests by adding resources):
Microservices let you scale independently. If your inventory service needs 10x resources but your user service doesn't, you can scale them separately. That's valuable when you need it.
But it's not a performance optimization. It's a scaling strategy. And it comes with a tax.
The argument "microservices scale better" made more sense in 2010 when servers had 4-8 cores.
Modern servers have 32-128 cores. A single machine can run thousands of concurrent operations efficiently.
If your monolith is built with modern concurrent execution patterns, it can handle massive throughput on a single deployment. For example, using patterns like ephemeral execution coordinators, you can:
// Process thousands of concurrent operations in a monolith
services.AddEphemeralWorkCoordinator<TranslationRequest>(
async (request, ct) => await TranslateAsync(request, ct),
new EphemeralOptions { MaxConcurrency = Environment.ProcessorCount * 4 });
// Bounded, observable, efficient concurrent processing
// No network overhead, no SerDe, no container orchestration
// Can handle 10k+ req/sec on a single machine
This gives you:
When you do need to scale beyond one machine, you can:
You're still running a monolith. You've just deployed it multiple times.
The point: Don't split into microservices for "performance". Split when independent scaling of specific components justifies the operational overhead.
Microservices don't reduce complexity. They redistribute it.
The "simple service" still needs context:
People underestimate this because diagrams hide it.
Every boundary becomes a contract.
Every contract becomes:
You can dodge this for a while with "just deploy everything together".
That's the punchline: if you deploy everything together, you built a monolith. Just a worse one.
The early spend is always the same:
None of this ships product value.
And most teams do it before they've proven the product deserves the complexity.
This is the central mistake: you pay the ceremony tax before you've earned the value. Like daily standups that waste time without delivering alignment, microservices can become ritual architecture: impressive to look at, expensive to maintain, and disconnected from the actual problem you're solving.
Taken together, these costs don't disappear - they compound. And they compound whether or not the organisation needed microservices in the first place.
Architecture exists to help groups of humans change software safely.
Not to impress other engineers.
Not to satisfy a diagram.
Not to justify a platform team you don't have.
Team size and deployment cadence matter more than the pattern catalogue.
Conway's Law isn't optional. It's physics.
Your architecture will mirror your communication structure whether you like it or not.
Microservices don't create autonomy. They require it.
Most systems should start as a monolith. But not a sloppy one.
A modular monolith is:
It means:
The point isn't to stay monolithic forever. The point is to earn boundaries before you make them remote.
A modular monolith forces you to learn the skills microservices pretend to solve:
If you can't build a clean modular monolith, microservices won't save you. They'll just distribute the mess.
The right monolith design lets you defer the microservices decision without locking yourself in.
One of the best examples is the outbox pattern - a way to achieve eventual consistency and async processing inside a monolith, with a clean path to distribution later.
Instead of:
// Tightly coupled synchronous code
public async Task PlaceOrder(Order order)
{
await _orderRepo.Save(order);
await _emailService.SendConfirmation(order); // Blocks on external service
await _inventoryService.Reserve(order.Items); // Blocks on another service
}
You write:
// Outbox pattern: write events to a table
public async Task PlaceOrder(Order order)
{
await using var transaction = await _db.Database.BeginTransactionAsync();
// Save order
await _orderRepo.Save(order);
// Write events to outbox table (same transaction)
_db.OutboxMessages.Add(new OutboxMessage
{
EventType = "OrderPlaced",
Payload = JsonSerializer.Serialize(order),
CreatedAt = DateTime.UtcNow
});
await _db.SaveChangesAsync();
await transaction.CommitAsync();
// Background worker picks up outbox events and publishes them
}
What this gives you:
The SegmentCommerce sample project demonstrates this pattern in production:
// Mostlylucid.SegmentCommerce/Services/Queue/PostgresOutbox.cs
public class PostgresOutbox
{
public async Task PublishAsync<T>(string eventType, T payload)
{
var message = new OutboxMessage
{
EventType = eventType,
Payload = JsonSerializer.Serialize(payload),
CreatedAt = DateTime.UtcNow
};
_db.OutboxMessages.Add(message);
// Caller commits transaction
}
}
// Background service
public class OutboxProcessor : BackgroundService
{
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
var pending = await _db.OutboxMessages
.Where(m => !m.Processed)
.OrderBy(m => m.CreatedAt)
.Take(100)
.ToListAsync();
foreach (var message in pending)
{
await ProcessMessage(message);
message.Processed = true;
}
await _db.SaveChangesAsync();
await Task.Delay(1000, stoppingToken);
}
}
}
This runs in a single app today. When you need to scale:
You've built microservices-ready infrastructure without paying the distribution tax.
None of these require distribution. All of them make distribution easier later.
Microservices make sense when the constraints are real, not aspirational.
The critical question isn't "should we use microservices?" It's: do the benefits outweigh the operational tax?
Like choosing between small local models and frontier LLMs, this is about understanding where complexity belongs and what failure modes you can afford.
If your reason contains the words might, eventually, or future-proof, it's probably not a reason.
Let's get concrete. Here's what changes when you split a monolith into services.
Monolith:
public async Task<Order> PlaceOrder(OrderRequest request)
{
var user = await _userService.GetUser(request.UserId);
var inventory = await _inventoryService.CheckStock(request.Items);
var price = _pricingService.Calculate(request.Items, user.Tier);
var order = new Order { /* ... */ };
await _orderRepository.Save(order);
await _emailService.SendConfirmation(order);
return order;
}
Total latency: ~50ms (in-process calls + 2 DB queries)
Microservices:
public async Task<Order> PlaceOrder(OrderRequest request)
{
// HTTP call to User Service (network + TLS + serialization)
var user = await _httpClient.GetAsync<User>($"http://user-service/users/{request.UserId}");
// HTTP call to Inventory Service
var inventory = await _httpClient.PostAsync<StockResult>(
"http://inventory-service/check", request.Items);
// HTTP call to Pricing Service
var price = await _httpClient.PostAsync<PriceResult>(
"http://pricing-service/calculate",
new { items = request.Items, tier = user.Tier });
// HTTP call to Order Service
var order = await _httpClient.PostAsync<Order>(
"http://order-service/orders", request);
// Event published to message bus
await _messageBus.Publish(new OrderPlaced { OrderId = order.Id });
return order;
}
Total latency: ~400ms (even optimistic 50–80ms per HTTP call in real environments + message bus publish ~20ms)
What you gained:
What you paid:
Monolith error handling:
try
{
var order = await PlaceOrder(request);
return Ok(order);
}
catch (InsufficientStockException)
{
return BadRequest(new { error = "Out of stock" });
}
catch (Exception ex)
{
_logger.LogError(ex, "Order placement failed");
return StatusCode(500);
}
Microservices error handling:
try
{
// Call User Service
var user = await _httpClient.GetAsync<User>($"http://user-service/users/{request.UserId}");
}
catch (HttpRequestException ex) when (ex.StatusCode == HttpStatusCode.NotFound)
{
return NotFound(new { error = "User not found" });
}
catch (HttpRequestException ex) when (ex.StatusCode == HttpStatusCode.ServiceUnavailable)
{
// Retry with exponential backoff?
// Circuit breaker opened?
// Fail fast or degrade gracefully?
_logger.LogWarning("User service unavailable, retrying...");
await Task.Delay(TimeSpan.FromMilliseconds(100));
// ... retry logic ...
}
catch (TaskCanceledException ex)
{
// Timeout - was the request processed? Do we retry?
_logger.LogError("User service timeout");
return StatusCode(503, new { error = "Service temporarily unavailable" });
}
try
{
var inventory = await _httpClient.PostAsync<StockResult>(
"http://inventory-service/check", request.Items);
}
catch (HttpRequestException ex) when (ex.StatusCode == HttpStatusCode.BadRequest)
{
// Business error from remote service
var errorDetails = await ex.Content.ReadAsAsync<ErrorResponse>();
return BadRequest(new { error = errorDetails.Message });
}
catch (HttpRequestException ex)
{
// Which service failed? Network issue? Service down?
// Do we have a fallback? Cached data? Fail fast?
_logger.LogError(ex, "Inventory service failed");
// Maybe try a backup instance?
// ... more retry logic ...
}
// And repeat for every service call...
Every network call introduces:
Monolith deployment:
# Build
dotnet publish -c Release
# Run migrations
dotnet ef database update
# Deploy
docker push myapp:v1.2.3
kubectl set image deployment/myapp myapp=myapp:v1.2.3
# Rollback if needed
kubectl rollout undo deployment/myapp
Microservices deployment:
You're changing the order structure. Now Order includes UserTier directly (denormalized for performance).
# 1. Deploy Pricing Service v2 (understands both old and new Order format)
kubectl set image deployment/pricing-service pricing-service=pricing:v2.0.0
# 2. Wait for rollout and monitor
kubectl rollout status deployment/pricing-service
# Check metrics - is v2 working with old order format?
# 3. Deploy Order Service v2 (starts sending new format)
kubectl set image deployment/order-service order-service=order:v2.0.0
# 4. Monitor for errors
# If Pricing v2 has a bug, you can't just rollback Order service
# You have to rollback both in reverse order
# 5. Deploy User Service v2 (stops including tier in response)
# But wait - old Order Service instances might still be running!
# Need zero-downtime rollout or maintain backward compat
# 6. Eventually clean up old code paths in Pricing Service v3
# (6 months later because you're scared to remove backward compat)
With microservices, every change crosses multiple services. Contract evolution requires:
None of this is impossible. But it requires discipline, tooling, and experience that most teams only earn after years of pain.
Monolith bug report: "Order placement fails for premium users"
// Set breakpoint in PlaceOrder
// Step through each call
// User tier is null - ah, there's the bug
// Fix, test, deploy
Microservices bug report: "Order placement fails for premium users"
# 1. Check logs - which service failed?
kubectl logs -l app=order-service --tail=100
# 2. Oh, it's calling Pricing service. Check those logs
kubectl logs -l app=pricing-service --tail=100
# 3. Grep for correlation ID across all services
stern -l app=order-service,app=pricing-service,app=user-service \
| grep "correlation-id-xyz"
# 4. Reconstruct the call chain from distributed traces
# Open Jaeger/Zipkin, find the trace
# User service returned 200 OK
# Pricing service returned 400 Bad Request
# Error: "user.tier is required"
# 5. Check User service - did it send tier?
# Look at schema version - ah, User v1.2 stopped sending tier
# When did that deploy? Was Pricing service updated?
# 6. Check API contracts
# Pricing expects tier, User stopped sending it
# Who approved this change?
# 7. Fix requires coordinating two teams
# Can't just deploy a fix - need contract negotiation
This is the reality: bugs that were 5-minute fixes become multi-team investigations.
If this sounds extreme, good. Microservices are extreme engineering.
Microservices are a one-way door. Treat them like one.
The safe path looks boring:
If you can't draw the boundary inside the monolith (with enforceable dependencies), you can't extract it safely.
Get the seams right locally first.
Reads are easier:
Move read models out first if you need separation.
Synchronous service calls create dependency chains.
Async messaging creates:
Start by separating events and facts, not by slicing endpoints.
No big bang.
No "we'll rewrite it properly".
Slice off a boundary, measure it, own it, and keep going.
If you can't explain why a service exists independently, it shouldn't exist at all.
Microservices are not a starting point. They are an outcome.
Complexity should be earned. Distributed systems are not a badge - they are a debt instrument.
The trade-off equation is simple:
Microservices Value = (Team Autonomy + Independent Scaling + Failure Isolation)
- (Latency Tax + SerDe Tax + Operational Overhead + Coordination Cost)
For most teams - especially early-stage or single-team products - the right side dominates. You pay enormous costs for benefits you don't need yet.
But when you have:
…then the left side starts to win. The tax becomes justified.
Ask these questions in order:
Can one team still own this end-to-end?
→ Yes: stay monolith. No: consider splitting.
Are teams blocked by each other's release cycles?
→ Yes: microservices might help. No: coordination is working.
Do we have the operational muscle to run distributed systems?
→ No: build it first. Yes: proceed carefully.
Can we trace, debug, and deploy multiple services without heroics?
→ No: you're not ready. Yes: you might be.
Have we proven the boundaries in code first?
→ No: fix your monolith structure. Yes: extraction is safer.
If you can't get past question 3 with confidence, you're not ready for microservices - and that's fine. Boring architecture is a competitive advantage.
Most successful products were built as monoliths first: GitHub, Shopify, Stack Overflow, Basecamp. They evolved into distributed systems only when the organisational pain demanded it.
Your job isn't to build the most impressive architecture. It's to deliver value while minimising accidental complexity.
And no customer has ever paid extra because your system used Kafka.
Sometimes that means microservices. Usually, it means a well-structured monolith and the discipline to keep it that way.
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