Interview Experience with American Express for a Go Developer Role

Recently, I had the opportunity to interview for a Go Developer position at American Express. The interview was comprehensive and covered verbal questions and practical tasks designed to assess my knowledge and proficiency with Go programming. Here’s a detailed account of my experience.

Verbal Questions

The interview began with a series of verbal questions aimed at evaluating my theoretical understanding of Go. Here are some of the key questions I was asked:

Q1: What is an interface in Go?

A1: In Go, an interface is a type that specifies a set of method signatures. It defines the behavior that a concrete type must implement. Interfaces promote polymorphism and decoupling in Go programs.

Q2: Can we embed an interface into another interface in Go?

A2: No, Go does not support embedding interfaces into other interfaces directly. However, you can embed interfaces into structs, but this is generally not recommended as it can lead to confusion.

Q3: What is the difference between a struct and an interface?

A3: In Go, a struct is a composite data type that groups together variables of different types under a single name. An interface, on the other hand, defines a set of method signatures that a type must implement to satisfy the interface. Structs provide a way to create custom data types with fields, while interfaces define behavior.

Q4: What is the defer keyword in Go?

A4: The defer keyword in Go is used to schedule a function call to be run after the surrounding function returns. It's commonly used to ensure that resources are properly released or cleanup actions are performed regardless of how the function exits (normally or due to an error).

Q5: Can we have a struct inside another struct in Go?

A5: Yes, Go allows you to define a struct inside another struct. This is known as a nested struct or embedded struct, and it's a way to compose more complex data structures.

Q6: What are Go routines?

A6: Go routines are lightweight threads of execution in Go. They are managed by the Go runtime and allow concurrent execution of functions. Go routines are more efficient than operating system threads, as they have lower overhead and can be multiplexed onto a smaller number of OS threads

.

Q7: What are Go channels?

A7: Go channels are a core feature of Go's concurrency model. They provide a way for Go routines to communicate and synchronize their execution. Channels are typed conduits through which you can send and receive values between Go routines, enabling safe communication and coordination.

Q8: What is Go context?

A8: Go context is a package (context) in Go that provides a way to pass cancellation signals, deadlines, and other request-scoped values across API boundaries and between Go routines. It's commonly used for managing the lifecycle and cancellation of operations in concurrent and networked applications.

Q9: How to avoid a race condition?

A9: Race conditions in Go can be avoided by synchronizing access to shared resources using synchronization primitives like mutexes or channels. By ensuring that only one Go routine can access a shared resource at a time, you can prevent data races and maintain the integrity of your program's state.

Q10: What is deadlock?

A10: Deadlock in Go occurs when two or more Go routines are waiting for each other to release resources that they need to proceed. This results in a situation where none of the Go routines can make progress, effectively halting the program's execution indefinitely.

Q11: What is a pointer and how does it help better than a normal variable?

A11: A pointer in Go is a variable that stores the memory address of another variable. Pointers allow you to indirectly access and manipulate variables, which can be useful for avoiding unnecessary copying of data and for managing memory more efficiently, especially when dealing with large data structures.

Q12: Do Go routines share the same memory or not?

A12: Yes, Go routines share the same memory address space within a single process. However, to ensure safe concurrent access to shared data, synchronization mechanisms like mutexes or channels should be used to prevent data races.

Q13: What is the sync package in Go?

A13: The sync package in Go provides synchronization primitives like mutexes, read-write locks, and conditions, which are essential for writing concurrent programs that access shared resources safely. It offers tools for coordinating the execution of Go routines and ensuring proper synchronization.

Q14: What is Mutex in Go?

A14: Mutex (short for mutual exclusion) in Go is a synchronization primitive used to protect shared resources from concurrent access by multiple Go routines. It allows only one Go routine at a time to access the protected resource, preventing data races and ensuring data integrity.

Practical Questions

After the verbal questions, the interview moved on to practical tasks where I had to demonstrate my coding skills in Go. Here are the key practical tasks I worked on:

Q1: How to return a JSON response in Go?

type Response struct {
    Message string `json:"message"`
}

func greetHandler(w http.ResponseWriter, r *http.Request) {
    response := Response{Message: "Hello, World!"}
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(response)
}

Q2: Accept data in query parameters and return a JSON response

func greetHandler(w http.ResponseWriter, r *http.Request) {
    name := r.URL.Query().Get("name")
    response := Response{Message: fmt.Sprintf("Hello, %s!", name)}
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(response)
}

Q3: Implement an interface with one method and implement it in two different types

type Greet interface {
    Greeting(name string) string
}

type FormalGreet struct{}

func (f FormalGreet) Greeting(name string) string {
    return fmt.Sprintf("How are you, %s?", name)
}

type InformalGreet struct{}

func (i InformalGreet) Greeting(name string) string {
    return fmt.Sprintf("Hey, %s!", name)
}

Q4: Accept an array of names in the request body and return a JSON array of greetings

type GreetingRequest struct {
    Names []string `json:"names"`
}

type GreetingResponse struct {
    Greetings []string `json:"greetings"`
}

func helloHandler(w http.ResponseWriter, r *http.Request) {
    if r.Method != http.MethodPost {
        http.Error(w, "Only POST requests are accepted", http.StatusMethodNotAllowed)
        return
    }

    var req GreetingRequest
    if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
        http.Error(w, "Invalid request body", http.StatusBadRequest)
        return
    }

    var greetings []string
    for _, name := range req.Names {
        greetings = append(greetings, fmt.Sprintf("Hello, %s!", name))
    }

    response := GreetingResponse{Greetings: greetings}
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(response)
}

Conclusion

The interview process at American Express was rigorous but fair, testing both my theoretical knowledge and practical skills in Go. I appreciated the balanced approach, as it allowed me to showcase my understanding of Go concepts as well as my ability to implement them in real-world scenarios.

Overall, the experience was positive and informative, providing me with valuable insights into what top-tier companies like American Express look for in Go developers. Whether or not I get the role, I feel more prepared for future interviews and have identified areas where I can continue to improve. If you're preparing for a Go Developer interview, I hope this account provides you with a useful roadmap for your preparation. Good luck!