Shadowing Practice: What Is REST API? Examples And How To Use It: Crash Course System Design #3 - Learn English Speaking with Video

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REST is the most common communication standard between computers over the internet.
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What is it?
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Why is it so popular?
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Let's take a look.
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API stands for Application Programming Interface.
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It is a way for two computers to talk to each other.
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The common API standard used by most mobile and web applications to talk to the servers is called REST.
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It stands for Representational State Transfer.
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It is a mouthful.
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What does that mean?
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REST is not a specification.
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It is a loose set of rules that has been the common standard for building web APIs since the early 2000s.
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An API that follows the REST standard is called a RESTful API.
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Some real-life examples are Twilio, Stripe, and Google Maps.
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Let's look at the basics of REST.
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A RESTful API organizes resources into a set of unique URIs or Uniform Resource Identifiers.
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The URIs differentiate different types of resources on a server.
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Here are some examples.
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The resources should be grouped by noun and not verb.
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An API to get all products should be slash products and not slash get all products.
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A client interacts with a resource by making a request to the endpoint for the resource over HTTP.
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The request has a very specific format as shown here.
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The line contains a URI for the resource we'd like to access.
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The URI is preceded by an XGTP verb, which tells the server what we want to do with the resource.
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A POST request means we want to create a new resource.
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A GET means we want to read the data about an existing resource.
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A PUT is for updating an existing resource.
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A DELETE is for removing an existing resource.
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You might have heard the acronym CRUD.
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This is what it stands for.
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In the body of these requests, there could be an optional HTTP request body that contains a custom payload of data, usually encoded in JSON.
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The server receives the request, processes it, and formats a result into a response.
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The first line of the response contains the HTTP status code to tell the client what happened to the request.
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A well implemented RESTful API returns proper HTTP status codes.
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The 200 level codes mean the request was successful.
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The 400 level codes mean something was wrong with our request.
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For example, the request contained incorrect syntax.
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At the 500 level, it means something ran wrong at the server level.
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For example, the service was unavailable.
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A well-behaved client could choose to retry a fail request with a 500 level status quo.
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We said could choose to retry because some actions are not idempotent and those require extra care when retrying.
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When an API is idempotent, making multiple identical requests has the same effect as making a single request.
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This is usually not the case for a post request to create a new resource.
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The response body is optional and could contain the data payload and is usually formatted in JSON.
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There's a critical attribute of REST that is worth discussing more.
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A REST implementation should be stateless.
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It means the two parties don't need to store any information about each other, and every request and response is independent from all others.
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This leads to web applications that are easy to scale and well-behaved.
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There are two final points to discuss to round out a well-behaved RESTful API.
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If an API endpoint returns a huge amount of data, use pagination.
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A common pagination scheme uses limit and offset as parameters.
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Here is an example.
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If they are not specified, the server should assume sensible default values.
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Lastly, versioning of an API is very important.
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allows an implementation to provide backward compatibility so that if we introduce breaking changes from one version to another,
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consumers can get enough time to move to the next version.
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There are many ways to version an API.
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The most straightforward is to prefix the version before the resource on the URI.
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For instance, like this.
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Restful API is simple and effective when applied sensibly.
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It may not be the best choice for all companies, but it is simple and good enough, and that's why it is so widely used.
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There are other popular API options like GraphQL and GRPC.
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We'll discuss those and compare them in separate videos.
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If you would like to learn more about system design, check out our books and weekly newsletter.
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Please subscribe if you learned something new thank you so much and we'll see you next time

Vocabulary and speaking notes for this lesson

This video has 65 sentences and 753 words to shadow. The speech runs for 5:11. The speaker talks at a steady 145 words per minute, a comfortable pace for shadowing. Only 78% of the words are among the 3,000 most common in English, so the vocabulary is demanding.

Key vocabulary in this video

15 words from the video worth learning, with pronunciation and meaning:

WordPronunciationMeaning
resource noun/ɹɪˈzɔːs/Something that one uses to achieve an objective, e.g. raw materials or personnel.
server noun/ˈsɝvɚ/A program that provides services to other programs or devices, either in the same computer or over a computer network.
format noun/ˈfɔːɹ.mæt/The layout of a publication or document.
behave verb/bɪˈheɪv/To conduct (oneself) well, or in a given way; to conform.
implementation noun/ˌɪmplɪmənˈteɪʃən/The process of moving an idea from concept to reality. In business, engineering and other fields, implementation refers to the building process rather than the…
optional adjective/ˈɑp.ʃə.nəl/Not compulsory; left to personal choice; elective.
verb noun/vɝb/A word that indicates an action, event, or state of being.
compare verb/kəmˈpɛɚ/To assess the similarities and differences between two or more things [“to compare X with Y”]. Having made the comparison of X with Y, one might have found it…
custom noun/ˈkʌstəm/Frequent repetition of the same behavior; way of behavior common to many; ordinary manner; habitual practice; method of doing, living or behaving.
introduce verb/ˌɪntɹəˈdus/To cause (someone) to be acquainted (with someone else).
default noun/dɪˈfɔlt/The condition of failing to meet an obligation.
identical adjective/ɪˈdɛntɪkl̩/Bearing full likeness by having precisely the same set of characteristics; indistinguishable.
implement verb/ˈɪmpləmənt/To bring about; to put into practice; to carry out.
interact verb/ɪn.təˈɹækt/To engage in communication and other shared activities (with someone).
subscribe verb/səbˈskɹaɪb/To write (one’s name) at the bottom of a document; to sign (one's name).

Phrasal verbs you will hear

WordMeaning
check out verbTo record the departure or withdrawal of someone or something (such as guests, employees, books, etc.).

Pronunciation to watch

The speaker uses 4 contractions and reduced forms, such as we'll, don't, we'd. Say them the short way, as you hear them.

  • The “sh” and “zh” sounds: implementation /ˌɪmplɪmənˈteɪʃən/, optional /ˈɑp.ʃə.nəl/, differentiate /dɪf.əˈɹɛn.ʃi.eɪt/, pagination /ˌpæd͡ʒəˈneɪʃən/
  • Long words — get the stress right: implementation /ˌɪmplɪmənˈteɪʃən/, unavailable /ˌʌnəˈveɪləbəl/, differentiate /dɪf.əˈɹɛn.ʃi.eɪt/, compatibility /kəmˌpætəˈbɪlɪti/, parameter /pəˈɹæm.ə.tɚ/

How to practise with this video

  1. Listen to the whole video once without speaking and note the words you do not know.
  2. Shadow it sentence by sentence at normal speed, repeating each one until your rhythm matches the speaker.
  3. Record yourself and compare with the original, paying attention to words like resource, server, format.

What is the Shadowing Technique?

Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.

Shadowing technique: read the full step-by-step guide →