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UDP is a message protocol, whatever the user writes is treated as a unit. Problem is we are restricted by data link transmission unit (called MTU). IP which carries UDP can be fragmented, to break that large message into smallest MTU. You can also disable fragmentation but

A request is like an arrow. its maximum speed is as it leaves the bow, then it slows down due to air and gravity. A request is at its maximum speed as it leaves the frontend’s NIC, then starts to slow down as it travels through network devices, proxies, the backend kernel, and.

Operating systems (their kernel specifically) orchestrate many processes, allow access to memory, disk, network and execute processes by scheduling them to the CPU. Sounds simple when we put it this way but this task is vast. Writing efficient programs depends on how much

Building a correct and performant transactional system requires deep knowledge in database fundamentals, application context and workflows. First correctness: It is the skill to scope operations into atomic transactions while managing concurrency of those operations to ensure a.

Lets talk about TCP blackhole, a fascinating network phenomenon. You see, IP fragmentation was created to allow large packets to pass through middle routers with smaller MTU (maximum transmission unit) than the sender. This quickly created performance and security problems.

Any code you write has a flaw, It might not be obvious today, but it will reveal itself one day. Google, Microsoft, Amazon and others all experienced severe outages during the pandemic. Because they didn’t anticipate the unique workload, they had to rewrite and redesign quite a.

Windows Kernel vs Linux Kernel when the port is unreachable (but the host is). Notice that Windows will return the failure in 2 seconds, while Linux returns immediately. This is exacerbated when you have both IP protocol families. You can use curl, telnet, ssh all have the same

The Anatomy of Node Packages.

Whoever initiates TCP FIN leaves its socket in TIME_WAIT state for any pending packets to arrive from the remote. If you attempt reuse the same address/port the bind will fail. Unless the SO_REUSEADDR is set on the socket. curl doesn’t set SO_REUSEADDR by default, thus the

Sometimes you have to make pragmatic decisions to keep the software consistent and predictable. This one is an interesting discussion on an issue in curl project upon forcing reuse local address port reuse when the socket is in timewait state.

Microsoft IIS implementation of HTTP/2 is weird. Often when the backend accepts h2, it sends a SETTINGS frame telling the client the maximum number concurrent streams it supports. IIS doesn’t do that, which then Chrome interprets as the server supports unlimited concurrent.

HTTP/1.1 protocol can mask inefficiently authored frontends. This is because of the browser connection pool limit (6-10 connections per domain). Once the backend advertises HTTP/2 or even 3, the floodgates opens and up to 200 requests can be sent concurrently. This can tax the.

I enjoy reading public bug reports, especially if it relates to an error am looking up. some much good stuff, this one an h2 GO AWAY frame incompatible implementation between client and backend.

SQL update or delete statements are interesting. The row locks held by those queries in a transaction can cause blocking. In some systems (SQL Server) page locks can be taken instead, causing even more blocking. Switching the order of the statement so its closer to the.

With the right index, MIN or MAX can be as cheap as a single IO (to the lowest or highest leaf btree page). Without an index, it can thrash your buffers and cpu. COUNT and AVG on the other hands are not as cheap.

ktls is brilliant. TLS encryption/decryption often happens in userland. While TCP lives in the kernel. With ktls, userland can hand the keys to the kernel and the kernel does crypto. When calling write, the kernel encrypts the packet and send it to the NIC. When calling.

An interesting case of the CORS. Backend returned the allow-origin header but so did the load balancer. Browser gets two headers with the same name, different values and throw this error. header contains multiple values but only one is allowed.

Best practices should have a “best by” date. They sometimes go bad, often in production. They are very useful but be willing to toss them at anytime and make your own best practices and forge your path. Because situations and tech change. and when you are on a new path, you.

A client connects to a database server and sends a query. Before the query is scheduled, the client crashes. What can happen next?. A good conversational question for networking, backend and database implementation. To make it more interesting, add a load balancer between the.

A key in Architecting efficient backends is networking. It is the bridge between frontend and the backend. Depending on the use case and the workflow, the engineer asks questions such as: What protocols should be used? What web servers, proxies, runtimes to deploy? What