👋 Hey {{first_name|there}},
Stop Launch and Pray
You’ve probably lived this: big refactor, new provider, shiny rewrite. Staging looks fine, synthetic tests pass, confidence feels high. You flip traffic, and immediately discover the thing only fails with real users, real data skew, real chaos. Cue the incident channel.
There’s a calmer way:
Shadow traffic and dual-run let you prove a replacement in parallel, using the exact traffic patterns and edge cases your system actually sees without risking users.
This is the natural next step after our recent lessons:
Reversibility (Lesson #18): design the exit before the entry.
Idempotency (Lesson #19): make retries and replays safe.
Backpressure (Lesson #20): keep the core path alive under stress.
SLOs & Error Budgets (Lesson #21): ship with guardrails.
Shadow + dual-run ties them together: you validate in production conditions while your kill switch stays within reach.
Let’s make reliability a number your team can actually use.
🧭 The Mindset Shift
From: “Launch and see what breaks.”
To: “Prove it in parallel and cut over deliberately.”
And also:
From “staging truth” → to “production truth.”
From “correctness on paper” → to “behavior parity under reality.”
From “we think it’s faster” → to “we measured it against the SLO you care about.”
Dual-run isn’t an extra ceremony; it’s how you trade unknown risk for measured evidence.
🎯 Want to learn how to design systems that make sense, not just work?
If this resonated, the new version of my free 5-Day Crash Course – From Developer to Architect will take you deeper into:
Mindset Shift - From task finisher to system shaper
Design for Change - Build for today, adapt for tomorrow
Tradeoff Thinking - Decide with context, not dogma
Architecture = Communication - Align minds, not just modules
Lead Without the Title - Influence decisions before you’re promoted
It’s 5 short, focused lessons designed for busy engineers, and it’s free.
Now let’s continue.