No Database No Retention No Party

One month ago I wrote this article You don’t need a database, a queue, a distributed system: Go is enough. and I posted it on HackerNews.

The result was interesting: it generated quite a bit of discussion and a lot of people decided to play with Binary Duel.

The Good

Number of games

At a certain point, there were from 80 to 150 contemporary games and everything was good: no errors, the Golang backend was behaving in the best way. ( 🎉 wohooo 🎉)

I was right, what an engineer!

The Bad

After this initial boom, only a few people decided to revisit the game (approx 10 a day).

The solution

The solution is quite trivial: we need a db, need login, need a leaderboard, we need a way to incentivize competition between users, and a ranking system.
And that is exactly what we have done! And again, Golang comes with a special treat:

You don’t actually need any dependency to do what you want, you can just code it.

We needed a way to cache the leaderboard since it is quite expensive to build.

Building a leaderboard is expensive and difficult to maintain it updated.
So once we get it, we need to cache it. So, here is how you can implement a simple route cache (in memory) with TTL:

type CacheEntry struct {
    cachedResponse interface{}
    t0             time.Time
var routeCache map[string]CacheEntry
if cEnt, ok := routeCache["<cache-key>"]; ok && time.Since(cEnt.t0) < TTL {
    // return response cached
} else {
    // produce response
    routeCache["<cache-key>"] = value

We needed a way to bulk write operations to save precious free tier operations.

So here is how you can implement a ticker to bulk save games and assign points in the database

go func() {
    for {
        time.Sleep(CLEANING_WINDOW_SECONDS * time.Second)

I am having so much fun using this stack and implementing it all in this artisanal way. And I am looking forward to the moment the scale will force me to rewrite it all!

Will all of this manage to increase retention?

Do you have any ideas or comments to improve Binary Duel?

Leave them under this HK post or email me via

Stay tuned!