Deep Dive
I have watched two engineers argue for twenty minutes about whether keep alive was enabled. One was looking at a Connection: keep-alive header. The other was looking at net.ipv4.tcp_keepalive_time. They were both right and they were talking about different layers of the stack. The naming
Docker
One changed byte early in a Dockerfile throws away everything after it. Here is how the cache key is computed and how to order instructions so it survives.
PostgreSQL
Dead tuples that never get reclaimed, a table twice the size of its data, and queries getting slower every week. Here is what blocks vacuum and how to see it.
MicroVMs
The bug only reproduces with real state. Copying the database loses the parts that matter. Cloning the whole machine keeps them.
DevOps
Lag climbing on one partition while the rest keep up tells you something specific. Here is how to read the numbers before you add consumers that cannot help.
MicroVMs
Query times doubling at unpredictable hours with no deploy and no traffic spike. When the cause is not in your process, it is usually not on your machine either.
Deep Dive
Traditional VMs take thirty seconds. Firecracker takes 125 milliseconds. The difference is everything it refuses to do.
Performance
Width is time, stacking is call depth, and left to right means nothing. Once those three facts land, flame graphs become the fastest way to find a bottleneck.
Debugging
Setting a breakpoint rewrites your program's machine code while it runs. Here is the mechanism, from the 0xCC byte up to why conditional breakpoints are slow.
Debugging
When your profiler shows nothing and your logs are silent, strace shows you every syscall with timings. Here is a practical subset worth knowing.
Docker
The difference between a container and a microVM is one sentence long, and almost every isolation decision follows from it.