Your slowest ten queries are a twenty-minute report
The claim Before you scale up the database instance, add a read replica, or rewrite an endpoint, run one query. In almost every under-performing application we are asked to look at...
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Engineering
Engineering notes, infrastructure deep dives and practical guides from the Exotecho team.
Store money as integer cents, never as a float
The claim A floating-point number cannot represent ten cents exactly, so any system that stores money in a float column will, given enough transactions, produce totals that are off...
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Put a UUID on the invoice before you need it
The claim Give every business record a stable, public-safe identifier at the moment it is created, separate from its database primary key. The auto-incrementing integer is fine ins...
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Offset pagination lies to you after page fifty
The claim LIMIT 20 OFFSET 5000 has two defects, and the well-known one is the lesser. Yes, it gets slower linearly, because the database must produce and discard five thousand rows...
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Every feature flag needs a deletion date
The claim A feature flag is a deployment tool with a lifespan measured in weeks. A flag that survives past its launch becomes permanent configuration nobody understands, and a code...
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Every timeout must be shorter than the one in front
The claim Most cascading outages are not caused by a component failing. They are caused by a component being slow while every timeout in the stack is longer than the one upstream o...
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Structured logs with a request ID, or none at all
The claim Free-text log lines without a correlation identifier are not diagnostic data. They are a diary. During an incident you cannot answer the only question that matters — what...
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Never send email from inside a web request
The claim Any call to a third-party service inside a request handler makes that service a hard dependency of your application. Sending mail synchronously means your order confirmat...
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Images, not JavaScript, are what your pages weigh
The claim On a typical content or commerce site, images account for the majority of transferred bytes — usually 55% to 75% — and the fix is a build step you configure once, not a f...
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