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The SQL Server Iceberg

Above water: “The query is slow.”
Below: everything else.

Steer your diver down along the iceberg. Every station holds a real workload problem. You get one life – one wrong answer and you’re fish food. And at the very bottom, in R’lyeh, Cthulhu sleeps: three correct answers in a row, or he eats you.

Click or tap – the diver swims there. Answer with a click or the keys 1 to 4.

How to play

One life, 15 questions, six zones.

Everyone knows the iceberg picture: on top you see “the application is slow”, underneath lies everything that really slows SQL Server down. The game takes you down, from mistakes everyone has seen to internals that rarely come up.

  1. Dive in and steer: click or tap into the scene and the diver swims there. The next station glows; an arrow points to it when it is out of view.
  2. One question per station: twelve stations in five zones, each with one question and four answers. Your air is your time, 60 to 44 seconds depending on the zone.
  3. One mistake ends the dive. So does running out of air. The zone’s creature gets you; afterwards you see the correct answer.
  4. Points: deeper zones are worth more, fast answers add up to 50 percent, and a streak of correct answers can double the value. Twice, the lifeline “Read the execution plan” removes two wrong answers.
  5. Cthulhu waits at the very bottom: three questions from the deepest zone in a row. Answer all of them and you get 5,000 bonus points.
The six zones

What waits at which depth.

51 questions from real-world work, sorted by depth. Every dive draws its questions anew.

  • 0 to 25 m

    The Tip

    What everyone sees: SELECT *, NOLOCK, cursors, AUTO_SHRINK, missing indexes, max server memory.

  • 25 to 110 m

    The Shallows

    Indexes and statistics: key lookups, CONVERT_IMPLICIT, ascending keys, fill factor, forwarded records.

  • 110 to 220 m

    Twilight Zone

    Plans, parameters and memory: parameter sniffing, spills, memory grants, row goals. Related: Understanding the optimizer.

  • 220 to 320 m

    Midnight Zone

    Locks, latches and waits: deadlocks, lock escalation, THREADPOOL, PAGEIOLATCH, WRITELOG.

  • 320 to 434 m

    The Abyss

    Internals: spinlocks, last page insert, Halloween protection, VLFs, forced plans in Query Store.

  • from 434 m

    R’lyeh

    What should never have been awakened: online rebuilds, Accelerated Database Recovery, parallelism deadlocks. Three questions in a row, no mistakes allowed.

Share your result

How deep did your colleagues get?

After your dive you can share your result on LinkedIn or copy the link.

When you dive in, the game fetches its question sequence from psg-stack.com; at the end it sends your answers there. The server recalculates score and depth itself and creates a result page under a random key. It stores the result, language and time, no name and no answer history; there is no public leaderboard. Your previous dives are remembered only by your browser on this device. Details are in our privacy policy.

Understanding the optimizer More articles