Implement user favourites service (Go challenge) #1

parath · 2025-09-25T10:37:26Z

Adds an implementation of user favourites with REST API and tests.

pmantafounis-gwi

Hi @parath, thank you very much for taking the time to complete the challenge. Overall, your implementation was clear, and easy to follow!

I've added some comments on my side, for you to take a look when you have the time :)

pmantafounis-gwi · 2025-09-30T11:33:53Z

Dockerfile

+RUN go build -o favourites main.go
+
+# Runtime stage
+FROM alpine:3.22


Thanks! 🙏

pmantafounis-gwi · 2025-09-30T11:40:49Z

internal/httpapi/server.go

+	r.HandleFunc("/favourites/{userId}", s.getFavouritesHandler).Methods("GET")
+	r.HandleFunc("/favourites/{userId}", s.addFavouriteHandler).Methods("POST")


having {userId} as a resource identifier in favourites feels ambiguous. How could you restructure the endpoints to convey the ownership better and make it a bit more restful?

Good point, using {userId} in the path is ambiguous. A more RESTful design would be /users/{userId}/favourites, which makes ownership explicit. In a real system I would also rely on authentication/authorization (e.g. JWT) to derive the user context, which would allow simplifying to /favourites.

pmantafounis-gwi · 2025-09-30T11:42:14Z

internal/httpapi/server.go

+	f.ID = s.store.NextFavouriteID()
+	created, err := s.store.AddFavourite(f)


can you spot any issues with calling s.store.NextFavouriteID() before s.store.AddFavourite(f)? If yes how would you solve them?

Nice catch! Calling NextFavouriteID() separately could potentially cause inconsistencies under concurrency or service failures.
A safer approach would be to generate the ID inside AddFavourite so the operation is atomic. In a production setup with a database, I would let the DB assign IDs (via sequences/UUIDs) to ensure consistency.

pmantafounis-gwi · 2025-09-30T11:46:51Z

internal/httpapi/server.go

+func writeError(w http.ResponseWriter, r *http.Request, status int, msg string, code ErrorCode) {
+	logRequest(r, fmt.Sprintf("status=%d code=%s msg=%s", status, code, msg))
+	writeJSON(w, status, apiError{Error: msg, Code: code})
+}


Are there any other ways for logging the requests without having to always use this custom function across the codebase?

Yes there are other ways, while the helper works, a standardized solution would be the preferred approach.
Middleware-based logging or a structured logging library like zap or logrus would avoid custom calls across handlers and give more consistent logs.

pmantafounis-gwi · 2025-09-30T12:02:38Z

README.md

+## Assumptions
+- REST API endpoints to fetch, add, remove and update assets in favourites list.
+- JSON request/response with lower-camel JSON keys (id, userId, assetId, assetType, description, assetData, createdAt, updatedAt).
+- In-memory store for the challenge purposes. No data store persistence present. Stored data are lost on restart.


How would you model it in a database? What DB would you use and with what schema?

For persistence, I would align with the platform’s existing DB solution.
Assuming Postgres, I would model it like:

CREATE TABLE favourites ( id TEXT PRIMARY KEY, user_id TEXT NOT NULL, asset_id TEXT NOT NULL, asset_type TEXT NOT NULL, description TEXT, asset_data JSONB NOT NULL, created_at TIMESTAMP NOT NULL, updated_at TIMESTAMP NOT NULL, UNIQUE(user_id, asset_id) );

JSONB gives flexibility for asset data while enabling indexing.
The unique (user_id, asset_id) constraint enforces the same rule as in the in-memory store.

lkslts64

@parath Thanks for submitting the Go challenge, we really appreciate your effort. You delivered a clean and pragmatic solution featuring easy-to-read documentation and robust test coverage.

Below, I have prepared some questions for you to check ☺️

lkslts64 · 2025-09-30T13:31:43Z

internal/favourites/model.go

+	AssetID     string          `json:"assetId"`
+	AssetType   AssetType       `json:"assetType"`
+	Description string          `json:"description,omitempty"`
+	AssetData   json.RawMessage `json:"assetData"`


What’s the reason behind opting for json.RawMessage type here instead of []byte ?

Great question! I chose json.RawMessage because it makes the intent explicit: the field holds JSON. It avoids extra (un)marshalling steps compared to []byte when embedding JSON blobs and integrates directly with Go’s encoding/json.

lkslts64 · 2025-09-30T13:32:34Z

main.go

+func main() {
+	r := httpapi.NewServer(favourites.NewInMemoryStore())
+	log.Println("Server listening on :8080")
+	log.Fatal(http.ListenAndServe(":8080", r))


log.Fatal is used to terminate the server immediately when the process receives a signal. How would you modify your server to shutdown gracefully? Why graceful shutdowns matters in a Kubernetes environment? And finally, how would a non-graceful server termination impact in-flight requests that write to the in-memory store?

Absolutely! Graceful shutdowns are important in Kubernetes where pods are terminated during scaling or updates. Without it, in-flight requests could be dropped and writes to the in-memory store lost.
In the current solution I use http.ListenAndServe, but for production I would wrap this in an http.Server and handle Shutdown(ctx) to catch OS signals and let ongoing requests finish cleanly.

lkslts64 · 2025-09-30T13:33:16Z

main.go

+)
+
+func main() {
+	r := httpapi.NewServer(favourites.NewInMemoryStore())


If you were to add some HTTP middleware to this app, what would that be?

The first I would add is structured request logging. Authentication/authorization middleware would also be essential once the service is integrated into the platform.

lkslts64 · 2025-09-30T13:40:04Z

internal/favourites/store.go

+
+// InMemoryStore stores favourites in memory per user
+type InMemoryStore struct {
+	mu     sync.RWMutex


Great to see that you use a RW mutex 👏

🙏 Thanks!

parath · 2025-10-02T07:24:21Z

@pmantafounis-gwi @lkslts64 Thanks a lot for the thoughtful review. 🙏
I ’ve added my responses inline.

This was a great exercise and I really appreciate the feedback, as it helped me reflect on both design and production aspects.
Appreciate the time you both took to review this, it was a great learning experience!

parath added 9 commits September 11, 2025 17:34

favourites REST API server and tests

39b86d4

removed globals and created structure

32038ec

adds JSON tags and creates a simple error model

30f2326

adds logging and uses error model

118e0e2

adds error code type

bac59cd

moves update time to store and housekeeping

073403e

tiding up timestamps and tests

44d23cd

consistency in README

31ac8cf

adds README note

771d5cd

pmantafounis-gwi reviewed Sep 30, 2025

View reviewed changes

lkslts64 reviewed Sep 30, 2025

View reviewed changes

		r.HandleFunc("/favourites/{userId}", s.getFavouritesHandler).Methods("GET")
		r.HandleFunc("/favourites/{userId}", s.addFavouriteHandler).Methods("POST")

		f.ID = s.store.NextFavouriteID()
		created, err := s.store.AddFavourite(f)

Implement user favourites service (Go challenge) #1

Are you sure you want to change the base?

Implement user favourites service (Go challenge) #1

Uh oh!

Conversation

parath commented Sep 25, 2025

Uh oh!

pmantafounis-gwi left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

pmantafounis-gwi Sep 30, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

parath Oct 2, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lkslts64 left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lkslts64 Sep 30, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

parath commented Oct 2, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

pmantafounis-gwi Sep 30, 2025 •

edited

Loading

parath Oct 2, 2025 •

edited

Loading

lkslts64 Sep 30, 2025 •

edited

Loading