Building a Bank with Go - QCon London March 2017

Traditionally applications have been built as monoliths; single applications which become larger and more complex over time, which limit our ability to react to change. An example of this is the banking industry where mergers and acquisitions between banks have lead to a patchwork of different systems & technologies that cost billions of dollars per year to maintain. As a result, the pace of innovation in the banking industry has slowed to a crawl. At Monzo we're building a new kind of bank backed by a microservice platform written in Go. In this talk we'll look at why Go is perfectly suited to this style of architecture, the language features that make it particularly attractive to high volume, low latency, distributed applications, and how easy it is to adopt into existing systems and organisations.

Transcript

1. Building a Bank
   with Go
   Matt Heath, Monzo
   

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2. Hi, I’m Matt
   @mattheath
   

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5. monoliths
   traditional dev
   

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6. A UK banking licence is authorised by the PRA and
   regulated by the PRA and FCA1, allowing deposit-
   taking and balance sheet lending. Once granted,
   it allows firms to passport across Europe, accessing
   This is followed by a “mobilisation” phase during
   which final capital is raised and IT systems are
   completed, before launching to the public.
   We received a UK banking licence in August 2016!
   FEB
   2015
   JAN
   2016
   JAN
   2017
   MAR FEB FEB
   APR MAR MAR APR MAY JUN JUL
   MAY APR
   JUN MAY
   JUL JUN
   AUG JUL
   SEP AUG
   NOV SEP
   DEC NOV DEC
   PRE APPLICATION APPLICATION MOBILISATION LAUNCH
   LICENCE WITH
   RESTRICTIONS
   50K MAX
   DEPOSIT
   WE ARE
   HERE
   

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15. ?
    

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16. Application
    

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17. Application
    Database
    

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18. Application
    Database
    

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19. Application
    Databases
    

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20. Application
    Databases
    Search
    

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21. Application
    Databases
    Search
    Caching
    

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22. Application
    Databases
    Search
    Caching
    CAT GIFS
    

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23. ALL
    HAIL
    THE
    MONOLITH
    

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25. Application
    Databases
    Search
    Caching
    CAT GIFS
    

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26. APPLICATION
    Application
    

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29. Single Responsibility
    Principle
    

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30. Bounded Context
    

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31. Well defined
    Interfaces
    

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33. Why Go?
    Memory Managed
    Statically Typed
    Excellent Concurrency
    Perfect for simple, small, network services
    

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34. Lightweight
    Concurrency
    

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35. Goroutines
    

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36. // Blocking function call
    handleRequest()
    

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37. // Function runs concurrently
    go handleRequest()
    

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38. package main
    func main() {
    go handleRequest()
    // …
    }
    

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39. package main
    func main() {
    go handleRequest()
    // …
    }
    main
    

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40. package main
    func main() {
    go handleRequest()
    // …
    }
    handleRequest
    main
    

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41. "Do not communicate by
    sharing memory; instead, share
    memory by communicating."
    - Effective Go
    

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42. Channels
    

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47. Simplicity
    

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48. Static Linking
    Stdlib
    etc
    

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49. 0
    40
    80
    160
    120
    Feb
    2015
    Mar
    2017
    200
    Number of services
    

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52. monzo/typhon
    

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53. Service
    Service
    

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54. Service
    Service
    Transport
    

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55. Service
    Service
    Transport
    Service
    Service
    

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56. Service
    Service
    Transport
    Service
    Service
    Client library
    Server library
    

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57. Service
    Service Service
    Service
    HTTP
    HTTP
    

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58. Service Discovery
    Load Balancing
    Timeouts and Expirations
    Retries
    Rate Limiting
    Connection Pooling
    Circuit Breaking
    Failure Detection
    Metrics and Tracing
    Interrupts
    Context Propagation
    

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59. Service
    Service Service
    Service
    HTTP
    HTTP
    ?
    

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60. Service
    Service Service
    Service
    HTTP
    HTTP
    linkerd
    

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61. Service Discovery
    Load Balancing
    Timeouts and Expirations
    Retries
    Rate Limiting
    Connection Pooling
    Circuit Breaking
    Failure Detection
    Metrics and Tracing
    Interrupts
    Context Propagation
    

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62. Load Balancer
    

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63. Load Balancer
    HTTP API & Routing Layer
    

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64. Load Balancer
    HTTP API & Routing Layer
    API

    Service
    

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66. /webhooks —-> Webhook API
    

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67. Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    

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68. Auth

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    

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69. Auth

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    Database
    

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70. Database
    Auth

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    Database
    

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71. External
    Provider
    Database
    Auth

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    Database
    

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72. type Service func(req Request) Response
    

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73. router.GET("/", List)
    router.POST("/", Register)
    router.DELETE("/:id", Deregister)
    

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74. Making our
    service reliable
    

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75. + =
    ❤
    

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77. Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    

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78. Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    

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79. Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    

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80. Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Webhook

    Service
    Load Balancer
    HTTP API & Routing Layer
    Webhook

    API
    Slow or

    Errors
    

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81. Event Driven
    Architecture
    

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82. Service
    A
    Service
    B
    Load Balancer
    HTTP API & Routing Layer
    API
    Service
    

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83. API
    Service
    Service
    A
    Service
    B
    Load Balancer
    HTTP API & Routing Layer
    

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84. API
    Service
    Service
    A
    Service
    B
    Load Balancer
    HTTP API & Routing Layer
    

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85. API
    Service
    Service
    A
    Service
    B
    Load Balancer
    HTTP API & Routing Layer
    Service
    C
    Service
    D
    Service
    E
    

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86. Context
    Propagation
    

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87. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    

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88. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    

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89. 8096820c-3b7b-47ec-bce6-1c239252ab40
    

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90. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    

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91. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    

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92. package context
    type Context interface {
    Deadline() (deadline time.Time, ok bool)
    Done() <-chan struct{}
    Err() error
    Value(key interface{}) interface{}
    }
    

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93. package context
    type Context interface {
    Deadline() (deadline time.Time, ok bool)
    Done() <-chan struct{}
    Err() error
    Value(key interface{}) interface{}
    }
    

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94. package context
    type Context interface {
    Deadline() (deadline time.Time, ok bool)
    Done() <-chan struct{}
    Err() error
    Value(key interface{}) interface{}
    }
    

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95. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    

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96. api
    api
    api.customer
    api.customer
    service.customer
    service.customer
    SEND
    RECV
    SEND
    RECV
    RECV
    SEND
    RECV
    SEND
    

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97. api api.customer service.customer
    SEND
    RECV
    SEND
    RECV
    RECV
    SEND
    RECV
    SEND
    phosphor
    

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99. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
    API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
    

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100. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     

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101. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     

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102. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     

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103. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     

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105. API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     API card-api card-processing cards transactions balance transaction-enrichment merchant feed-generator feed apns
     

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108. Perfect for

     microservice
     architectures
     

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109. Concurrency:

     Goroutines
     Channels
     

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110. Small
     Simple
     Easy
     

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111. Thanks!
     @mattheath
     @monzo
     

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