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README.md
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README.md
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:information_source: This repo contains questions and exercises on various technical topics, sometimes related to DevOps and SRE :)
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:bar_chart: There are currently **1726** questions
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:bar_chart: There are currently **1750** questions
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:books: To learn more about DevOps and SRE, check the resources in [devops-resources](https://github.com/bregman-arie/devops-resources) repository
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@ -5575,16 +5575,28 @@ The Terraform Registry provides a centralized location for official and communit
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### Containers Self Assesment
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<details>
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<summary>What is a Container? What is it used for?</summary><br><b>
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<summary>What is a Container?</summary><br><b>
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Containers are a form of operating system virtualization. A single container might be used to run anything from a small microservice or software process to a larger application. Inside a container are all the necessary executables, binary code, libraries, and configuration files, making them easy to ship and run with same expected results on different machines.
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This can be tricky to answer since there are many ways to create a containers:
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- Docker
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- systemd-nspawn
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- LXC
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If to focus on OCI (Open Container Initiative) based containers, it offers the following [definition](https://github.com/opencontainers/runtime-spec/blob/master/glossary.md#container): "An environment for executing processes with configurable isolation and resource limitations. For example, namespaces, resource limits, and mounts are all part of the container environment."
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</b></details>
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<details>
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<summary>Why containers are needed?</summary><br><b>
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OCI provides a good [explanation](https://github.com/opencontainers/runtime-spec/blob/master/principles.md#the-5-principles-of-standard-containers): "Define a unit of software delivery called a Standard Container. The goal of a Standard Container is to encapsulate a software component and all its dependencies in a format that is self-describing and portable, so that any compliant runtime can run it without extra dependencies, regardless of the underlying machine and the contents of the container."
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</b></details>
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<details>
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<summary>How are containers different from virtual machines (VMs)?</summary><br><b>
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The primary difference between containers and VMs is that containers allow you to virtualize
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multiple workloads on the operating system while in the case of VMs the hardware is being virtualized to run multiple machines each with its own OS.
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multiple workloads on a single operating system while in the case of VMs, the hardware is being virtualized to run multiple machines each with its own guest OS.
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You can also think about it as containers are for OS-level virtualization while VMs are for hardware virtualization.
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* Containers don't require an entire guest operating system as VMs. Containers share the system's kernel as opposed to VMs. They isolate themselves via the use of namespaces and cgroups
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@ -5596,14 +5608,26 @@ You can also think about it as containers are for OS-level virtualization while
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<summary>In which scenarios would you use containers and in which you would prefer to use VMs?</summary><br><b>
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You should choose VMs when:
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* you need run an application which requires all the resources and functionalities of an OS
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* you need full isolation and security
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* You need run an application which requires all the resources and functionalities of an OS
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* You need full isolation and security
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You should choose containers when:
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* you need a lightweight solution
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* You need a lightweight solution
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* Running multiple versions or instances of a single application
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</b></details>
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<details>
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<summary>What is the OCI?</summary><br><b>
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OCI (Open Container Initiative) is an open governance established in 2015 to standardize container creation - format, runtime, etc. At that time there were a number of parties involved and the most prominent one was Docker.
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</b></details>
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<details>
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<summary>Which operations OCI based containers must support?</summary><br><b>
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Create, Kill, Delete, Start and Query State.
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</b></details>
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#### Containers - Architecture
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<details>
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@ -6573,6 +6597,33 @@ True (and not only the Pods but anything else it created).
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True. When the label, used by a ReplicaSet in the selector field, removed from a Pod, that Pod no longer controlled by the ReplicaSet and the ReplicaSet will create a new Pod to compensate for the one it "lost".
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</b></details>
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<details>
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<summary>How to scale a deployment to 8 replicas?</code></summary><br><b>
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kubectl scale deploy <DEPLOYMENT_NAME> --replicas=8
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</b></details>
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#### Kubernetes - Storage
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<details>
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<summary>What is a volume in regards to Kubernetes?</summary><br><b>
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A directory accessible by the containers inside a certain Pod. The mechanism responsible for creating the directory and managing it, ... is mainly depends on the volume type.
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</b></details>
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<details>
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<summary>Which problems volumes in Kubernetes solve?</summary><br><b>
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1. Sharing files between containers running in the same Pod
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2. Storage in containers is ephemeral - it usually doesn't last for long. For example, when a container crashes, you lose all on-disk data.
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</b></details>
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<details>
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<summary>Explain ephemeral volume types vs. persistent volumes in regards to Pods</summary><br><b>
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Ephemeral volume types have the lifetime of a pod as opposed to persistent volumes which exist beyond the lifetime of a Pod.
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</b></details>
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#### Kubernetes - Network Policies
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<details>
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@ -6824,42 +6875,6 @@ metadata:
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and you can verify with: `kubectl get configmap -n some-namespace`
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</b></details>
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#### Kubernetes Commands
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<details>
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<summary>What <code>kubectl exec</code> does?</code></summary><br><b>
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</b></details>
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<details>
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<summary>What <code>kubectl get all</code> does?</code></summary><br><b>
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</b></details>
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<details>
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<summary>What the command <code>kubectl get pod</code> does?</code></summary><br><b>
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</b></details>
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<details>
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<summary>How to see all the components of a certain application?</code></summary><br><b>
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`kubectl get all | grep [APP_NAME]`
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</b></details>
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<details>
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<summary>What <code>kubectl apply -f [file]</code> does?</code></summary><br><b>
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</b></details>
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<details>
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<summary>What the command <code>kubectl api-resources --namespaced=false</code> does?</code></summary><br><b>
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Lists the components that doesn't bound to a namespace.
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</b></details>
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<details>
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<summary>How to print information on a specific pod?</code></summary><br><b>
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`kubectl describe pod pod_name`
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</b></details>
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<details>
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<summary>How to execute the command "ls" in an existing pod?</code></summary><br><b>
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@ -6886,12 +6901,6 @@ kubectl run nginx --image=nginx --restart=Never --port 80 --expose
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<summary>Why to create kind deployment, if pods can be launched with replicaset?</summary><br><b>
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</b></details>
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<details>
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<summary>How to scale a deployment to 8 replicas?</code></summary><br><b>
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kubectl scale deploy some-deployment --replicas=8
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</b></details>
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<details>
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<summary>How to get list of resources which are not in a namespace?</code></summary><br><b>
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@ -6976,7 +6985,7 @@ False. CPU is a compressible resource while memory is a non compressible resourc
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Explained [here](https://www.youtube.com/watch?v=i9V4oCa5f9I)
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</b></details>
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#### Kubernetes Operator
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#### Kubernetes - Operators
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<details>
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<summary>What is an Operator?</summary><br><b>
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@ -7250,6 +7259,16 @@ The pod is automatically assigned with the default service account (in the names
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`kubectl get serviceaccounts`
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</b></details>
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#### Kubernetes - Patterns
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<details>
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<summary>Which containers pattern is used in the following drawing?</summary><br><b>
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</b></details>
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<details>
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<summary>Explain the sidecar container pattern</summary><br><b>
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</b></details>
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#### Kubernetes - Misc
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<details>
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@ -7572,6 +7591,10 @@ True
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<summary>What is "Duck Typing"?</summary><br><b>
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</b></details>
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<details>
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<summary>Explain string interpolation</summary><br><b>
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</b></details>
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##### Common algorithms
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<details>
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@ -12371,7 +12394,17 @@ document_number: 2
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```
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</b></details>
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#### Jira
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#### Customers and Service Providers
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<details>
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<summary>What is SLO (service-level objective)?</summary><br><b>
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</b></details>
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<details>
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<summary>What is SLA (service-level agreement)?</summary><br><b>
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</b></details>
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## Jira
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<details>
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<summary>Explain/Demonstrate the following types in Jira:
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@ -12385,7 +12418,7 @@ document_number: 2
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<summary>What is a project in Jira?</summary><br><b>
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</b></details>
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#### Kafka
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## Kafka
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<details>
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<summary>What is Kafka?</summary><br><b>
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@ -12402,7 +12435,7 @@ percentage ratio
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</summary><br><b>
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</b></details>
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#### Cassandra
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## Cassandra
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<details>
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<summary>When running a cassandra cluster, how often do you need to run nodetool repair in order to keep the cluster consistent?
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@ -12413,17 +12446,7 @@ percentage ratio
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</summary><br><b>
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</b></details>
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#### Customers and Service Providers
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<details>
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<summary>What is SLO (service-level objective)?</summary><br><b>
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</b></details>
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<details>
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<summary>What is SLA (service-level agreement)?</summary><br><b>
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</b></details>
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#### HTTP
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## HTTP
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<details>
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<summary>What is HTTP?</summary><br><b>
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@ -13024,7 +13047,7 @@ Bonus: extract the last word of each line
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## System Design
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<details>
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<summary>Explain what is a "Single point of failure" and give an example</summary><br><b>
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<summary>Explain what is a "Single point of failure"?</summary><br><b>
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</b></details>
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<details>
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