Charles Xu
Essays, books, wiki on technologies, career, markets, and more.
Category git
We all know Google employs a version tracking system that uses a single repository/depot. Every close-source google product that you love is tracked by this single repo, which is so...
Git is one of the most widely used version control systems. Traditionally, a repository on git is considered as a complete history of the entire project in the form of...
Committing often and pushing often has been advocated as good practice when using Git, which saves your latest work on remote even if your hard drive dies right after and...
Category web
Imagine you run a single page app at example.com that communicates with backends over restful API and is authenticated with JWT tokens managed by you, but identities are managed by...
Imagine your app is doing tremendously well with growing traffics. If there is a single server for your app, and the server is approaching its capacity, how would you scale...
HTTP provides an abstraction of short connections. Unlike the continuous byte streams in TCP, exchanges between client and server over HTTP starts with a client request and ends with server...
A common design for content display, pagination partitions information into multiple pages and serves one at a time. We have seen it in search results, message history, and cascading news...
I have been working with another three wonderful people on the senior design project, which is a web application of an inventory management system, and the production is up at...
All teams will henceforth expose their data and functionality through service interfaces. There will be no other form of inter-process communication (IPC) allowed: no direct linking, no direct reads of...
Category microservices
As presented in my previous post, microservices are the state-of-the-art architecture for building scalable, highly-available, manageable backend. No more 30-minute build time, single point of failure, and constant regression from...
Message queues are an asynchronous inter-process communication protocol that gains much of its glory with the recent hypes in microservices. Senders and receivers do not interact with the middleware at...
All teams will henceforth expose their data and functionality through service interfaces. There will be no other form of inter-process communication (IPC) allowed: no direct linking, no direct reads of...
Category distributed systems
Imagine your app is doing tremendously well with growing traffics. If there is a single server for your app, and the server is approaching its capacity, how would you scale...
Git is one of the most widely used version control systems. Traditionally, a repository on git is considered as a complete history of the entire project in the form of...
Here is where we stand. Fisher-Lynch-Patterson has shown that consensus is not guaranteed in bounded time in a purely asynchronous network. The CAP theorem shows that from consistency, availability, and...
Remote Procedure Call (RPC) is a canonical structuring paradigm for client-server/request-response services.
Category signal processing
We all share the sorrow and misery from that signal processing class. You were thrown at some crazy formula, kind of know how to use them but probably never understand why...
Category istio
Kubernetes does not differentiate sidecars and application containers in a Pod. Hence, enabling Istio for short-running workloads imposes additional challenges to the conventional approach of injecting an Envoy sidecar to...
As presented in my previous post, microservices are the state-of-the-art architecture for building scalable, highly-available, manageable backend. No more 30-minute build time, single point of failure, and constant regression from...
We all know Google employs a version tracking system that uses a single repository/depot. Every close-source google product that you love is tracked by this single repo, which is so...
Category security
In the world of internet, sending messages in clear text is like swimming naked. We would love some secure communication channels free from eavesdropping or tampering. Security as such is...
Category docker
Introduced in version v17.05, multi-stage builds feature in Dockerfiles enables you to create smaller container images with better caching and smaller security footprint. Fundamentally, the new syntax allows one to...
Many regard containers as a virtualization technology. They are missing out. Docker has much more to offer. It is a graceful solution to some of the most painful experience in...
Category interview
Imagine your app is doing tremendously well with growing traffics. If there is a single server for your app, and the server is approaching its capacity, how would you scale...
Category kubernetes
We go from containers and network namespace to Pod-to-Pod, Pod-to-Service, and external-client-to-Service networking.
My team at Cruise operates tens of Kubernetes clusters with 10,000s cores and 100s of TB of RAM. Since migration to GCP, we have hit several interesting scaling issues. One...
Pods in Kubernetes are the smallest orchestration unit and are ephemeral by definition: Deployment/StatefulSet/DaemonSet/ReplicaSet updates or patches Nodepool downscaling (compaction) or upgrades (cordoned and drained)
Summary To achieve zero-downtime service update, Kubernetes rolling update implies the API must be both forward and backward compatible. Forward compatibility is hard if at all makes sense. Blue-green update...
It is common to extract the application configuration to a separate file as a runtime dependency of the container image that includes the application binary. As a result, the same...
Category operation
Summary To achieve zero-downtime service update, Kubernetes rolling update implies the API must be both forward and backward compatible. Forward compatibility is hard if at all makes sense. Blue-green update...
It is common to extract the application configuration to a separate file as a runtime dependency of the container image that includes the application binary. As a result, the same...
Category networking
We go from containers and network namespace to Pod-to-Pod, Pod-to-Service, and external-client-to-Service networking.
DNS prefers UDP. There are times when DNS must run on TCP (request or response size exceeds a single packet, perhaps due to too many response records), but UDP is...
A super quick recap, one’s complement represents negative x by reverting every bit of x, while two’s complement negative x as one’s complement of x plus 1. Symbolically,
Category career
Disclaimer: Opinions are my own. Not investment advice.
This post explains the expectation of each engineering level in the most concise and company-agnostic way and reveals the steps towards promotion.
Unlike in school when we get grades on every assignment and in every course, we get less frequent feedback in professional life, usually once or twice per year, which is...
When I was a kid playing chess with my dad, he sometimes would offer me hints on some good moves. I would never make those moves. I would rather make...
Category go
Unlike C++ or Python, Go does not support function parameters with default values if unspecified. Specifically, we want that
Category shell
I hope you find inspirations from these pretty neat shell tricks and my shell setup.
Category investment
Disclaimer: Opinions are my own. Not investment advice.
Category law
Notes on Intellectual Property (IP) law for founders and busy professionals. Not legal advice. For informational purposes only. Laws can change, so this article may contain dated information. Always consult...
Category startup
Notes derived from a guest lecture by Danny Wallace, Partner at PwC’s Silicon Valley practice. For informational purposes only. Errors and omissions are my own.
Notes on Intellectual Property (IP) law for founders and busy professionals. Not legal advice. For informational purposes only. Laws can change, so this article may contain dated information. Always consult...
Category accounting
Notes derived from a guest lecture by Danny Wallace, Partner at PwC’s Silicon Valley practice. For informational purposes only. Errors and omissions are my own.
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