GWI – Favorite Assets Service (Engineering Challenge Submission) by alexkazan87 · Pull Request #55 · GlobalWebIndex/platform-go-challenge

alexkazan87 · 2025-11-27T12:20:35Z

This Pull Request delivers the implementation for the GlobalWebIndex (GWI) engineering challenge. It provides a fully functional HTTP service that allows authenticated users to manage their personal list of favorite assets (charts, insights, audiences). The solution includes:

JWT-based authentication and role-based authorization
In-memory storage for users, tokens, and favorites
Preloaded demo users: alice (user) and bob (admin)
Complete CRUD API for managing favorites
Structured, layered architecture (domain, application, infrastructure, HTTP)
Consistent JSON error responses
Example cURL commands and API documentation in Solution.md
Dockerfile for running the service in a container

Fix ctx userid Add dockefile

alexandros-georgantas

Hello @alexkazan87 👋 ,

Thank you for taking the time working on this assignment!
I have left some comments on this PR and it would be great if you find the time to address them!

Thanks,
Alex

alexandros-georgantas · 2025-12-05T12:10:24Z

+RUN CGO_ENABLED=0 GOOS=linux go build -o favorites ./cmd/main.go
+
+FROM alpine:3
+WORKDIR /root/


Could you suggest any enhancements for the application image? e.g. security

alexandros-georgantas · 2025-12-05T12:12:26Z

+	@echo "Please use 'make <target>' where <target> is one of the following:"
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
+
+run: ## Run the application


Could you please argue about your decision of including the vendor folder in general? What are you trying to achieve and what is the need in the context of this assignment?

alexandros-georgantas · 2025-12-05T12:14:45Z

+
+func main() {
+	infraProviders := infra.NewInfraProviders()
+	tp := time.NewTimeProvider()


Could you please elaborate about the need of having these two providers (time and uuid)? What are the benefits of that? Are you using them consistently?

alexandros-georgantas · 2025-12-05T12:15:43Z

@@ -0,0 +1,20 @@
+module github.com/akazantzidis/gwi-ass


alexandros-georgantas · 2025-12-05T12:30:25Z

Could you please explain the purpose for this notification service in the scope of this assignment? What is the value added by this service?

alexandros-georgantas · 2025-12-05T12:32:58Z

+import (
+	"github.com/akazantzidis/gwi-ass/internal/app/auth/command"
+	"github.com/akazantzidis/gwi-ass/internal/app/favourite/commands"
+	queries2 "github.com/akazantzidis/gwi-ass/internal/app/user/queries"


What is the purpose of this queries2 module?

alexandros-georgantas · 2025-12-05T12:34:56Z

+	ID          uuid.UUID       `json:"id,omitempty"`
+	Type        AssetType       `json:"type"`
+	Description string          `json:"description"`
+	Data        json.RawMessage `json:"data"`


Could you suggest an alternative approach for modeling the entities required in this assignment? If you had more time how would you refactor this to make it more type safe?

alexandros-georgantas · 2025-12-05T12:41:49Z

+)
+
+var (
+	jwtKey               = []byte("secret")


In a production environment how would you have handled that?

alexandros-georgantas · 2025-12-05T12:45:09Z

+	appServices := app.NewServices(infraProviders.FavoriteRepository, infraProviders.NotificationService, infraProviders.UserRepository, infraProviders.RefreshTokenRepository, up, tp)
+
+	infraHTTPServer := infra.NewHTTPServer(appServices)
+	infraHTTPServer.ListenAndServe(":8080")


In a production env how would you have handled that? Please suggest an alternative solution to this implementation.

alexandros-georgantas · 2025-12-05T12:47:19Z

+
+	appServices := app.NewServices(infraProviders.FavoriteRepository, infraProviders.NotificationService, infraProviders.UserRepository, infraProviders.RefreshTokenRepository, up, tp)
+
+	infraHTTPServer := infra.NewHTTPServer(appServices)


Please explain what will happen if something goes wrong during the initialization of the server? Is there any alternative more graceful handling that could be implemented?

pamanta

Hi @alexkazan87,

Thank you very much for taking the time to complete the assignment.

I've also left some comments for you to have a look when you have time :)

pamanta · 2025-12-05T15:12:53Z

+	favorite, err := h.repo.GetByID(command.UserID, command.ID)
+	if err != nil {
+		return fmt.Errorf("failed to fetch favorite: %w", err)
+	}
+	if favorite == nil {
+		return fmt.Errorf("favorite with ID %s does not exist for user %s", command.ID, command.UserID)
+	}
+
+	// Update fields
+	favorite.Type = command.Type
+	favorite.Description = command.Description
+	favorite.Data = command.Data
+
+	// Persist the update
+	if err := h.repo.Update(command.UserID, *favorite); err != nil {
+		return fmt.Errorf("failed to update favorite: %w", err)
+	}
+
+	return nil


can you identify any concerns with this method? Particularly about race conditions and concurrency? If yes, how would you correct them in a production environment?

pamanta · 2025-12-05T15:19:30Z

+	}
+}
+
+type Favorite struct {


How is the relation between user -> favorite established in the designed model? Can you elaborate a bit on how would you model this differently into a DB?

pamanta · 2025-12-05T15:49:44Z

+	var req CreateFavoriteRequestModel
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		helper.WriteJSONError(w, http.StatusBadRequest, fmt.Errorf("invalid request body"), nil)
+		return
+	}


In the current implementation, a chart favorite could have the same data structure as an insight or audience without any differentiation or validation. What concerns does this raise in production and how would you address them if you had more time?

pamanta · 2025-12-05T16:08:35Z

+	fav, err := c.favoriteServices.Queries.GetFavoriteHandler.Handle(
+		queries.GetFavoriteRequest{
+			UserID:     userID,
+			FavoriteID: favoriteID,
+		},
+	)
+
+	if err != nil {
+		helper.WriteJSONError(w, http.StatusInternalServerError, err, nil)
+		return
+	}
+	if fav == nil {
+		helper.WriteJSONError(w, http.StatusNotFound, fmt.Errorf("favorite not found"), nil)
+		return
+	}


Could you trace what happens here when a favorite does not exist for a user? Are there any issues? If yes, how would you fix it and how would you ensure this doesn't occur again in the future?

akazantzidis added 11 commits November 23, 2025 13:02

add initial solution - clean architecture

c245fdf

Add lock mechanism - protecting critical segments

877e71e

add secuirty layer

6ab7613

protect users

3b0f6fd

Add doc

ab50d8a

Fix ctx userid Add dockefile

removed corrupted file

64d0fa0

fixed favorite remove

c797cae

Returns empty list

e3a8e22

Add assetType validation

e6df018

Clear curls in md

50262a6

Add more explanations how to get userId after user initialization

d36d019

alexandros-georgantas reviewed Dec 5, 2025

View reviewed changes

pamanta reviewed Dec 5, 2025

View reviewed changes


		appServices := app.NewServices(infraProviders.FavoriteRepository, infraProviders.NotificationService, infraProviders.UserRepository, infraProviders.RefreshTokenRepository, up, tp)

		infraHTTPServer := infra.NewHTTPServer(appServices)

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alexkazan87 commented Nov 27, 2025

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