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Tech Flashcards

1
Q

What is Webpack?

A

Open-source JavaScript module bundler that takes modules with dependencies and generates static assets representing those modules?

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2
Q

What is Secure Shell?

A

The cryptographic network protocol for operating network services, such as remote command line login and remote command execution, securely over an unsecured network, connecting client to server?
(ssh user@serveraddress)

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3
Q

What is a shell?

A

User interface for access to an operating system’s services (GUI or CLI)?

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4
Q

What is the open source software that automates software provisioning, configuration management, and application deployment?

A

Ansible

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5
Q

What is operating system feature in which the kernel allows the existence of multiple isolated user-space instances?

A

Containerization (operating-system level virtualization)

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6
Q

What is a special relational database table column (or combination of columns) designated to uniquely identify all table records

A

Primary Key

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7
Q

What is the term describing a DB table representing a many-to-many relationship between two entities?

A

Join table (junction, linking, association table)

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8
Q

What are the YAML files that express configurations, deployment, and orchestration in Ansible, and allows Ansible to perform operations on managed nodes.

A

Ansible Playbooks

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9
Q

What are the description of the nodes that can be accessed by Ansible described by a configuration file, in INI or YAML format whose default location is in /etc/ansible/hosts?

A

Ansible Inventory

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10
Q

What is the quality of a distributed data store being able to continue operation despite an arbitrary number of messages being dropped or delayed by the network between nodes?

A

Partition tolerance (network partition)

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11
Q

What is Consistency?

A

The quality of a distributed data store where every read receives the most recent write or an error.

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12
Q

What is Availability?

A

The quality of a distributed data store where every request receives a (non-error) response – without the guarantee that it contains the most recent write.

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13
Q

What is a special relational database table column (or combination of columns) designated to uniquely identify all table records?

A

Primary key

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14
Q

What Javascript keyword always returns a promise and allows the usage of keyword “await” in it?

A

async

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15
Q

What Javascript keyword before a promise makes JS engine wait until that promise resolves and also behaves as a “throw error” clause?

A

await

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16
Q

What is is the maintenance of, and the assurance of the accuracy and consistency of, data over its entire life-cycle?

A

Data integrity

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17
Q

What is the process of structuring a relational database in order to reduce data redundancy and improve data integrity?

A

Database normalization

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18
Q

What occurs in database systems that have values repeated unnecessarily in one or more records or fields, within a table, or where the field is replicated/repeated in two or more tables?

A

Data redundancy

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19
Q

What is a Forward Proxy server and what is it used for?

A

What is a server that acts as an intermediary for requests from clients seeking resources from other servers, used to add structure and encapsulation to distributed networks. Provides anonymity to clients.

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20
Q

What is a Message queue?

A

Type of asynchronous service-to-service communication software component puts messages to be processed by one service consumer: so messages aren’t lost when a service fails, decouple heavyweight processing, to buffer or batch work, and to smooth spiky workloads?

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21
Q

What is First normal form (1NF)

A

Property of relational database is true if the domain of each attribute contains only atomic (indivisible) values, and the value of each attribute contains only a single value from that domain.

Example: Not having multiple telephone # per person in the same column or across multiple columns.

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22
Q

What is a dynamic-named value that can affect the way running processes will behave on a computer, that is specific to each process, that can be inherited from a parent process?

A

Environment variable

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23
Q

Second normal form (2NF)

A

Property of a relational database is true if it is in 1NF and every non-prime attribute of the relation is dependent on the whole of every candidate key?

Example: Part, Warehouse, Quantity, Warehouse_address. Address doesn’t belong, redundant and repeated.

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24
Q

What is an intermediary for its associated servers to be contacted by any client? It can hide servers behind it, do load balancing, caching, compressing.

A

Reverse proxy

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25
Q

What is a form of a database where it is in 2NF and all the attributes in a table are determined only by the candidate keys of that relation and not by any non-prime attributes. (None of the attributes are transitively dependent on each other)

A

Third normal form (3NF)

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26
Q

What is Redis?

A

An in-memory, nosql, key-value data structure used as a cache, database, and message broker.

It can sit between the server application and primary database to cache and speed records.

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27
Q

What is Sharding/Horizontal partitioning

A

Technique divides a database by putting different rows into different tables, potentially across each instance of a database schema, to improve index/search performance?

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28
Q

What are the three locations in order of Caching DNS records for a specific Time To Live(TTL)?

A

Browser, OS, and ISP recursive resolver.

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29
Q

What web development design pattern prevents duplicate form submissions as a result of page refreshing or bookmarking by returning a 302 Found response?

A

Post/Redirect/Get (PRG)

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30
Q

What is Network Address Translation (NAT)

A

The method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device? It is used in private networks to help conserving global IP address space.

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31
Q

What is Elasticsearch?

A

A distributed, Lucene-based, full-text search engine with an HTTP web interface and schema-free JSON documents?

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32
Q

What is the UNIX command to make a new directory?

A

mkdir name_of_directory

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33
Q

What is the UNIX command to used to update the access date or create a new file (without opening or saving it)?

A

touch

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34
Q

What is the UNIX command used to create a hard link or a symbolic link (symlink) to an existing file?

A

ln source_file target_file

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35
Q

What is the UNIX command used to remove objects such as computer files, directories and symbolic links from file systems?

A

rm (-recursive -verbose)

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36
Q

What is the UNIX command used to write the full pathname of the current working directory to the standard output? (print working directory)

A

pwd (-physical -logical)

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37
Q

What is Redundant Array of Independent Disks (RAID)?

A

What is the data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both.

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38
Q

What is the Unix command that moves one or more files or directories from one place to another?

A

mv file target_destination

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39
Q

What is an OS command that outputs the strings it is being passed as arguments? Commonly used to output status text to the screen in shell scripts.

A

echo (hello $USER)

40
Q

What is a OS command which enables a replacement of a word by another string, mainly used for abbreviating a system command, or for adding default arguments to a regularly used command?

A

alias myAlias=”arbitrary string”

41
Q

What logical gate returns a true output results if one, and only one, of the inputs to the gate is true? Also “one or the other but not both” or the inequality function.

A

XOR (exclusive OR)

42
Q

What OS command is used to mark variables and functions to be passed to child processes from a parent process?

A

export PATH=$PATH:/append/

43
Q

What is TCP (Transmission Control Protocol)?

A

Once a client has a IP address, what network protocol governs reliable, ordered, and error-checked delivery of a stream of data?

44
Q

What is a command-line utility for searching plain-text data sets for lines that match a regular expression?

A

Global Regular Expression Print

grep

45
Q

What is the first step in the main flow of a browser render engine?

A

Parsing

HTML and CSS files into a DOM and CSSOM tree.

46
Q

In a browser render main flow, what is the step after parsing the HTML and CSS into DOM and CSSOM that creates the elements that are actually visible?

A

Render Tree construction

47
Q

What step of the browser render main flow calculates position and size of elements in the render tree, using a dirty bit to determine what parent node hierarchy needs rendering?

A

Layout/Reflow

48
Q

What step of the browser render main flow traverses the completed render tree and actually displays and renders each element to the screen from the back of a stacking context to the front?

A

Painting

49
Q

What Unix directory contains system files such as startup scripts and user passwords?

A

/etc

50
Q

What is a subset of a computer’s hardware resources, virtualized as a separate computer?

A

LPAR/VM

51
Q

What is is computer software, firmware or hardware that creates and runs virtual machines by running on a host machine and creates guest VMs?

A

Hypervisor

52
Q

What is Jenkins?

A

What is an open source automation server with continuous integration that supports version control tools and triggers builds by various means?

53
Q

What is Docker?

A

Technology uses images as read-only templates to build instances called containers? To do so, it has a CLI client with [run, build] commands that communicates with a daemon (persistent process) on a host that listens for commands and manages images and containers.

54
Q

What is a pure function?

A

A function whose

  1. Return values are the same with the same input.
  2. No side effects (does not mutate local static or non-local vars)
55
Q

What is the function signature for Array.prototype.map?

A

arr.map(function callback(currentValue[, index[, array]])

56
Q

What is Agile in general?

A

Software development approach defined by self-organizing/cross-functional teams, adaptive planning, evolutionary development, early delivery, and continual improvement:

57
Q

What are the 5 stages of Waterfall software development?

A

Requirements, Design, Implementation, Testing, Maintenance.

58
Q

What are the 3 roles in Scrum?

A

Product owner, development team, Scrum master.

59
Q

What are the 5 stages of the Scrum workflow?

A

Sprint planning, Daily scrum, Sprint review, Sprint retrospective, Backlog refinement.

60
Q

What is WebSocket?

A

A computer communications protocol, providing full-duplex communication channels over a single TCP connection that allows server to send real-time messages with onMessage, and uses HTTP Upgrade header to establish itself.

61
Q

What is Vagrant and what are its components?

A

Tool for building virtual software dev environments, uses a Box/VM, Providers (Virtualbox, VMWare, AWS) where it runs, and a Provisioner (Ansible, Chef, Puppet) to configure the env.

62
Q

What is a Vagrantfile?

A

A configuration file that describes an environment including boxes used, networking, CPU and memory, providers used, shell scripts to run for provisioning among others.

63
Q

What is round-robin DNS? What are its drawbacks?

A

Load balancing technique where DNS authoritative nameserver rotates through a list of IPs. Drawbacks are client caching causing imbalanced load, and individual server unreliability.

64
Q

What is the outline/framework for a System Design problem?

A

Use Case, Interfaces, Constraints/Capacity, High Level Design, Data Model, Scalability

65
Q

What is data replication and two ways it can be done?

A

Storing data in more than one site to for redundancy, improve system availability. Can be done through transactional or snapshot.

66
Q

What is TLS?

A

Transport Layer Security (formerly SSL) is a cryptographic protocol that uses asymmetric key server auth, then symmetric-key encryption negotiated at start of connection to encrypt subsequent data. HTTPS is HTTP inside TLS, over port 443.

67
Q

What is caching and its trade off?

A

A hardware or software component that stores data so that future requests for that data can be served faster. Tradeoff between size and speed. Replacement policy can be FIFO, LRU

68
Q

What are three places/levels where caching can be implemented?

A

Application code, included in database as a feature, or in-memory RAM caches (Redis, Memcached).

69
Q

What happens when you type URL for a webpage and press enter?

A

DNS: Resolve address to IP using DNS (browser cache, OS cache, ISP).
TCP: Take URL/IP and port and opens TCP socket via OS, does SYN/SYN-ACK/ACK (TLS handshake happens next, public key encrypt for auth, then negotiate symmetric key for data)
HTTP(S): Client send HTTP request includes header with REST verb. Server responds with status code.
HTML: If it’s a webpage, browser parses HTML/CSS into DOM/CSSOM. Render Tree → Layout/Reflow → Painting the render tree

70
Q

What is a session and common example?

A

A temporary information communication between two systems. May use a cookie for authentication, saved user preference, or shopping cart information. In Rails, all session data is stored in client-side cookie, no server data.

71
Q

What are the 4 examples of Agile?

A

Individuals and Interactions over processes and tools
Working Software over comprehensive documentation
Customer Collaboration over contract negotiation
Responding to Change over following a plan

72
Q

When does a React component rerender?

A

Only when shouldComponentUpdate returns true, which it does by default for React.Component. Children do not automatically rerender when parent render.

73
Q

What is React PureComponent?

A

Same as React.Component, but implements shallow comparison (rather than auto-true) for shouldComponentUpdate. This means scalar value comparison, and reference comparison for objects.

74
Q

What React container composition approach passes child elements into generic components?

A

Containment

75
Q

What React container composition approach passes props from a more specific parent component into a more generic child component?

A

Specialization

76
Q

What are two purposes for security certificate?

A
  1. Identify verification

2. Encryption

77
Q

What are the steps of a TLS handshake?

A
  1. Client says hello (makes request).
  2. Server says here’s my CA-signed cert and my public key.
  3. Client uses browser-stored cert to verify and decrypt cert. Client generates and sends symmetric session key encrypted with server public key.
  4. Server decrypts with server-private and encrypts message with symmetric session key.
78
Q

What Dockerfile directive sources a container from online DockerHub?

A

FROM

79
Q

What Dockerfile directive runs an OS command in the container cmd line?

A

RUN

80
Q

What Dockerfile directive opens a port in the container?

A

EXPOSE

81
Q

What Dockerfile directive starts container?

A

CMD

82
Q

What are two UNIX commands that allow viewing system processes?

A

top

ps aux

83
Q

What UNIX command displays system IO info?

A

iostat

84
Q

What is the 7th layer of the OSI model? Why? How is it done?

A

Application Layer
Why: Allow apps communicate.
How: HTTP, SMTP, FTP.

85
Q

What is the 6th layer of the OSI model? Why? How is it done?

A

Presentation Layer
Why: Make data presentable to applications.
How: Translation (ASCII), encryption, compression (gzip).

86
Q

What is the 5th layer in OSI model? Why? How is it done?

A

Session Layer
Why: Opening & closing communication between devices, rightsizing connection.
How: Synchronization, Half or full duplexing.

87
Q

What is the 4th layer in OSI model? Why? How is it done?

A

Transport Layer
Why: Break message data into segments, flow control, error control.
How: TCP, UDP, and Ports.

88
Q

What is the 3rd layer in OSI model? Why? How is it done?

A

Network Layer
Why: Break segments into packets, move between inter-networks to right place.
How: Routing and addressing (IP)

89
Q

What is the 2nd layer in OSI model? Why? How is it done?

A

Data link layer
Why: Move packets between two nodes intra-network using framing, physical addressing.
How: Medium access control (MAC) and logical link control (LLC). ex: 802.3 Ethernet, 802.11 Wi-Fi

90
Q

What is the 1st layer in OSI model? Why? How is it done?

A

Physical layer - transmitting bits.

91
Q

What is a VLAN?

A

Broadcast domain partitioned at Layer 2 (Data link layer). Used to logically segment networks independent of physical structure (ex: company departments).

92
Q

What is Address Resolution Protocol? How?

A

Layer 2 Protocol to retrieve a physical MAC address from using a IP address.
How: Computer first checks ARP cache, if not found send ARP broadcast on network requesting MAC for IP. Dest computer answers.

93
Q

What is DHCP? Why?

A

Dynamic Host Configuration Protocol. Allows clients to retrieve and be dynamically assigned IP address.
Why: Automated, centralized, reuse/allocate IPs.

94
Q

What is a router? How does it function?

A

Device for forwarding packets at Layer 3 between networks.

How: Reads network packet header and uses routing table to forward the packet.

95
Q

WHAT is a network switch?

A

Device for connecting devices together in a network.

96
Q

What is KVM?

A

Kernel-Based Virtual Machine - Module lets Linux function as a hypervisor.

97
Q

HOW does a network switch function?

A

How: Layer 2 uses MAC addresses to send packet to right place.

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