/millions-click

Primary LanguageHTML

Click Batching Logic

The server keeps two counters in memory:

  • persistedCount: the total saved in MongoDB.
  • batchCount: the current batch accumulated in memory.

On each POST /click:

batchCount += 1
  • The API responds with totalClicks = persistedCount + batchCount so the UI updates immediately.
  Flush condition (batch size = 1000):
  When batchCount reaches 1000, the server:
  Atomically increments the MongoDB counter by 1000 using $inc.
  Updates persistedCount += 1000.
  Resets batchCount = 0.
  The response for that 1000th click reflects the new persisted total.
  • GET /clicks:
Returns { totalClicks: persistedCount + batchCount }.
  • Concurrency guard: A flushInProgress flag ensures only one flush occurs when multiple clicks hit the 1000 boundary at the same time.

Example flow:

Clicks 1–999:
batchCount: 1..999 (in memory only)
persistedCount: unchanged in DB
totalClicks = persistedCount + batchCount
Click 1000:
Writes +1000 to DB (atomic $inc)
persistedCount += 1000
batchCount resets to 0
totalClicks now equals the new persistedCount
Then the next 1000 clicks repeat the same cycle.

Note:

  • To change the batch size, update the condition and DB increment in index.js:
  • if (batchCount % 1000 === 0) -> switch to your desired threshold
{ $inc: { count: 1000 } } -> match the same threshold value