Terraform is fairly low-level software for managing your infrastructure. For instance, it’s used to create and provision cloud instances, networks and software. Unlike traditional tools in this area, Terraform is declarative. It means you don’t define step-by-step, imperative guides. Essentially, scripting your infrastructure with Bash or Python. Instead, you define desired, final infrastructure state. For example, how many hosts, how they should be connected, what kind of software and packages they should contain. Once you apply this configuration, Terraform takes all the necessary steps to fulfill your needs. Here’s how it works in more detail.

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Kubernetes is a platform for managing various workloads inside containers. Before I jump into a definition, let’s describe the problems it tries to solve. Imagine your application consists of several components. It can be microservices, multi-layer application, etc. Each type of component needs to be deployed on multiple servers. First of all, to support fault tolerance, but also to achieve horizontal scaling. Doing this by hand is quite problematic. Manually tracking which servers should host which components is tedious and error-prone. You need to take into account: * CPU and memory requirements of each component * discoverability (where each component is located) * provisioning (different components need different libraries and packages) * scaling out and migrating from broken servers * and so on, and so forth

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JavaScript language is primarily used inside

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REST is an architectural style of communication, based on HTTP. It was proposed in the year 2000 by Roy Fielding. In his dissertation he describes the way systems should communicate, embracing fundamental features of HTTP. He puts emphasis on: statelessness, support for caching, uniform representation and self-discoverability. APIs that adhere to these priniciples are called RESTful. This academic paper is quite abstract so I’ll focus on what it means in the enterprise. Also, it’s much easier to understand what RESTful API is when contrasted to SOAP. And GraphQL released recently.

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Disclaimer: this podcast is not about cryptocurrencies. I despise them. Instead, we’ll talk about asymmetric encryption. One of the most wonderful math discoveries of the 20th century. Before 1970s all cryptographic algorithms were symmetric. This means that the same key must be used to encrypt and decrypt data. That sounds rather obvious. If you encrypt a file with a password, you must use the same password to decrypt it. But there’s one problem. Imagine Bob wants to e-mail an encrypted file to Alice. Sadly, Eve can read all communication between Alice and Bob. File was encrypted, so no worries? Well, it’s not only encrypted, but also worthless. Alice doesn’t have a password. And how is Bob suppose to provide that password if Eve can spy all communication channels?

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Imagine two independent systems communicating with each other. One producing data and the other consuming it. There must be some place where data is buffered. Just in case the producer generated some data but the consumer is currently busy. For example, incoming requests, messages, packets - must wait. Sooner or later, this buffer overflows and either starts dropping data or crashes altogether. Moreover, large buffers imply growing latency between production and consumption. The consumer is perceived less responsive because data waited for a long time in queue. Especially when nothing is prioritized, so first come, first served. Also known as FIFO, first in, first out.

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Computers speak bits and bytes. Numbers in general. They don’t understand images, poems and JSON. When we say “hello”, it needs to be encoded to numbers. Conveniently, each character becomes one number. A number can then be stored, transfered and rendered on another computer. Therefore, everyone needs to agree which numbers represent which characters. The first commonly used attempt was called ASCII. American Standard Code for Information Interchange. In short, it’s a table of 127 symbols and their respective numbers. For example, lower-case h is 104, whereas exclamation mark is 33. There’s one problem here. 127 symbols. 7 bits. Of course, it’s an American Standard. So it ingores the existence of any other country and alphabet.

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When two processes run on the same machine, they are somewhat isolated. For example, they cannot read each other’s memory. However, they still share the same file system, libraries, network ports. And hardware: CPU and memory. Docker allows running processes with greater isolation on a Linux machine. Processes like: web servers, databases or web applications. Traditionally, to achieve better isolation, virtual machines were used. Virtual machine is essentially an operating system started inside of another operating system. For example, Windows running inside Linux. Typically you run a few VMs on a single host. Unfortunately, a virtual machine has an overhead. It takes several seconds to start and uses a significant amount of memory. Docker is somewhere in between. Better isolation than plain processes, but it’s not quite yet a VM.

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Domain name system (DNS for short) is one of the fundamental protocols of the Internet. In the Internet all communication is routed through IP addresses. Traditionally, these addresses consist of four numbers, like 91.198.174.192. Each and every server, as well as your computer, is identified using such an address. But we no longer remember phone numbers, let alone IP addresses! Remembering that the aforementioned IP belongs to wikipedia.org is tedious. DNS is often compared to a global phone book. A phone book that maps easy to remember domains like wikipedia.org or gmail.com to IP addresses - usable by machines. Without DNS the Internet could technically work. Just like you could use your phone without contacts, memorizing all phone numbers. DNS servers not only free us from remembering IP addresses. They know all of them.

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Before we fully appreciate how important HTTP cookies are, let’s imagine the web without them. HTTP is inherently stateless. This means that the HTTP server is not allowed and not capable of storing any context between requests. It has no memory of prior questions from the same client. Contrary to stateful protocols like FTP or SSH. They have a concept of long-running session. If you change the working directory during a session, subsequent commands take that into account. This is not the case for HTTP. For example, imagine you just logged in to GMail to see the list of unread e-mails. Now you click the most important one, from the Nigerian prince. Sadly, the server has no idea you are the person who just logged in. You must log in again. And again. This is where cookies help tremendously.

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