Performance
Two Hundred Redis Calls, and Every One Was a Round Trip
Each Redis command took a tenth of a millisecond to execute and a full round trip to deliver, and two hundred of them in a loop made the request slow while…
Tooling
openssl s_client Answers Every TLS Question
Chain broken, SNI wrong, protocol refused, certificate expiring. The TLS questions that produce guesswork are all answerable from one command, and the…
Deep Dive
TLS Session Resumption, and the Handshake That Never Got Faster
Resumption was enabled everywhere and the repeat handshakes were still full handshakes. Session tickets need a shared key across every backend, and behind a…
Code Review
Every Timeout Should Be Shorter Than the One Above It
A request chain is a ladder of deadlines, and when a lower rung is longer than the one above, the upper layer pays for work nobody will ever read.
Performance
Measuring TTFB When a CDN Is Answering for You
Your TTFB chart says forty milliseconds and your origin says four hundred. Both are true. The CDN is answering the measurements, so you are benchmarking the…
Error Autopsy
504 Gateway Timeout While Your Application Was Still Working
The proxy gave up at sixty seconds and returned a 504. The application finished at seventy four and wrote the result to nobody. Both were correct.
Security
The Rate Limit That Counted IPs and Not Accounts
The login rate limit was working perfectly and the credential stuffing succeeded completely. A per IP limiter is a defence against a single attacker, and a…
Tooling
lsof and ss Will Tell You Who Owns That Port
Port in use, connection stuck, file handle exhausted. Three of the most common production questions are answered by two old tools that read the kernel's own…
Deep Dive
HTTP/2 Fixed Head of Line Blocking, Then Reintroduced It
HTTP/2 multiplexed many streams over one connection to escape head of line blocking, then moved the blocking one layer down into TCP, where a single lost…
Error Autopsy
ETIMEDOUT, ECONNREFUSED, EHOSTUNREACH: Three Diagnoses
Three socket errors that read as 'the network is broken' are in fact three different answers to three different questions.
Performance
Brotli Saved Forty Percent on Text and Nothing on Your Images
Switching to Brotli produced a celebratory chart and almost no user benefit, because the payloads that dominate the page were already compressed.
Tooling
The curl Flag That Tells You Which Part of the Request Was Slow
A slow request is five possible slow things. One curl flag with a write-out template splits the total into DNS, connect, TLS, time to first byte and…