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Every free-to-play game has an economy. Gold, gems, energy, crafting mats — whatever you call them, they follow a simple rule: they flow in, and they flow out. If inflow and outflow are roughly balanced, the economy feels good. If they’re not, something goes wrong, often slowly, and often not noticed until it’s hurting revenue. This page defines the two ends of that flow and shows you how to instrument them so Qyren can monitor your economy.

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Faucet

A faucet is any way currency enters the economy. Examples:
  • A dungeon clear that rewards 500 gold.
  • The “daily login” bonus of 50 gems.
  • A quest reward of 200 gold and a rare gem.
  • A real-money purchase that grants 1,000 gems (yes — IAP is a faucet too).
  • A refund or compensation from customer support.
Every time any of these happens, you should log a currency_earned event:
The source field is free-form (your names), but be consistent. dungeon_reward and dungeon_clear will be treated as different faucets on your dashboard.

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Sink

A sink is any way currency leaves the economy. Examples:
  • Buying a sword in the shop for 2,000 gold.
  • Upgrading a hero for 500 gems.
  • Paying 100 gold to repair a broken weapon.
  • Skipping a timer with gems.
  • Converting soft currency into hard currency (this is a sink for gold and a faucet for gems).
Each removal gets a currency_spent event:

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Why the balance matters

A game that only faucets — where players earn currency faster than they can spend it — has an inflation problem. Three things will happen, in order:
  1. Currency stops feeling scarce. Early players don’t think about what to buy; they just buy everything.
  2. Late-game players run out of things to spend on. They sit on massive piles of gold with no use for it.
  3. When you release a new premium item, late-game players buy it instantly with the stockpile they already had — so your revenue per player drops.
A game that only sinks — where players can’t earn enough to keep up — has a grind problem. Players log off frustrated because their progress feels gated by tedious repetition. Whales may still pay through it; the rest churn. The sweet spot is a modest sink surplus: players spend slightly more than they earn from non-IAP sources, which makes IAP feel meaningful without being mandatory. Qyren tracks this as the Sink-to-Source Ratio, targeting 1.2 to 1.5.

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Worked example: Origins of Lume

Imagine a hypothetical game, Origins of Lume. Each player:
  • Clears 4 dungeons per day, earning 500 “lumens” (soft currency) per clear = 2,000 lumens/day faucet.
  • Gets a 200-lumen daily login = 200 lumens/day faucet.
  • Average total faucet per player per day: 2,200 lumens.
On the sink side, that same average player:
  • Spends 1,200 lumens/day on hero gear upgrades.
  • Spends 300 lumens/day on consumables (potions, revives).
  • Average total sink: 1,500 lumens/day.
Net inflow: +700 lumens/day per player. Multiplied across 10,000 DAU, that’s 7 million lumens per day entering circulation with no way out. Within a few weeks, the average player balance climbs. Within a few months, top-end balances are astronomical and your gem-to-lumen conversion shop becomes worthless. Qyren would flag this: sink-to-source ratio ≈ 0.68 (well below the healthy 1.2 floor), inflation rate rising, and recommendations like “add a 5,000-lumen repair cost to tier-5 gear” or “introduce a cosmetic-only lumen shop.”

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How to instrument, concretely

  1. Every time currency enters a player’s balance, log currency_earned including IAP grants. A missed faucet = false deflation signal.
  2. Every time currency leaves, log currency_spent. Include the sink name.
  3. Always send balance_after. This is how we detect ledger drift — if your events say a player earned 100 and spent 50 but balance_after shows +40, something is unlogged.
  4. Use consistent source and sink names. quest_reward everywhere, not sometimes quest_complete and sometimes quest_bonus.
  5. Log every currency separately. Gold, gems, event tokens, raid coins — each gets its own currency_type.

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Common mistakes

  • Forgetting small faucets. That 10-gold “first kill of the day” bonus looks trivial, but across a million players it’s the difference between healthy and inflationary.
  • Double-counting refunds. If you refund a purchase, log one currency_spent reversal — not both a spend cancellation and a new faucet. Pick one pattern and stick with it.
  • Bundling currencies. If a starter pack grants 100 gems and 5,000 gold, log two currency_earned events, not one with a composite amount.
  • Logging sinks before the spend actually clears. If a purchase fails, don’t log the sink. Log it on success only.
  • Using the same sink name for different mechanics. shop is too coarse. Prefer weapon_shop, hero_upgrade, timer_skip, etc. — you’ll want the breakdown later.
Once your currency events are flowing cleanly, the rest of Qyren’s economy features light up automatically. See Sink-to-Source Ratio and Inflation Rate next.