Every engineering influencer on Twitter is posting system design diagrams. Load balancers pointing to microservices pointing to message queues pointing to distributed caches. Boxes and arrows everywhere.
Meanwhile, their actual production system is a Django monolith on a single EC2 instance. And it works fine.
There's an entire industry built around system design content. YouTube videos breaking down "How Netflix handles 1 billion requests." LinkedIn posts about "designing Twitter from scratch." Interview prep courses charging $500 to teach you how to draw Kafka in a box.
Here's what nobody tells you: most engineers will never build systems at that scale.
Your startup has 1,000 users. You don't need Kafka. You don't need a service mesh. You don't need to "design for scale" when nobody's using your product yet.
But system design content is addictive. It makes you feel smart. Drawing architecture diagrams is more fun than fixing that flaky test that's been failing for three weeks.
I've interviewed candidates who could explain CAP theorem, consistent hashing, and leader election in distributed consensus. Whiteboard skills: impeccable.
Then I asked them to implement a simple rate limiter. They froze.
Twenty lines. Works for 99% of use cases. No Redis required.
System design knowledge without implementation skills is just trivia.
I'm not saying system design is useless. It matters when:
But for the other 95% of engineering work? Just build the thing. Refactor when it hurts. Scale when you need to. Most "scaling problems" are actually "nobody uses this" problems.
While everyone's studying system design, these skills are actually scarce:
Debugging production issues. Reading logs, tracing requests, finding the needle in the haystack at 3am. No diagram helps you here.
Writing maintainable code. Code that your teammates can understand. Code that you can understand six months later. Boring, undervalued, essential.
Shipping consistently. Breaking work into small pieces. Deploying multiple times a day. Not spending three months on "the architecture."
Understanding the business. Knowing why you're building what you're building. Cutting scope ruthlessly. Saying "we don't need that" instead of over-engineering.
None of these show up in system design interviews. All of them matter more for your actual job.
Study system design for interviews. It's a game with known rules.
But don't confuse interview prep with engineering skill. Don't spend hours watching "design Uber" videos when you've never built a side project that handles 100 concurrent users.
Ship something first. Scale it when it breaks.
The engineers I respect most aren't the ones with the best architecture diagrams. They're the ones who shipped working software while everyone else was still debating message queue choices.
System design is important. Shipping is importanter.
— blanho
Netflix ripped out Kafka, Cassandra, and three cache layers. Because every cache is a lie.
Most devs treat payments like CRUD. Then money disappears.
Everyone talks about clean code. Nobody talks about the feature that never shipped because someone was too busy renaming variables.
# What they studied
"In a distributed rate limiting scenario, we need to consider
Redis cluster partitioning, sliding window algorithms, and
eventual consistency trade-offs..."
# What the job actually needed
from collections import defaultdict
import time
class RateLimiter:
def __init__(self, max_requests, window_seconds):
self.max_requests = max_requests
self.window = window_seconds
self.requests = defaultdict(list)
def is_allowed(self, user_id):
now = time.time()
# Clean old requests
self.requests[user_id] = [
t for t in self.requests[user_id]
if now - t < self.window
]
if len(self.requests[user_id]) < self.max_requests:
self.requests[user_id].append(now)
return True
return False