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Track

Concurrency

Practice stale locks, duplicate workers, race conditions, async cleanup, and atomicity failures.

Skills trained

  • checkReason about interleavings
  • checkVerify lock cleanup
  • checkProtect idempotency

Recommended path

terminalThe Flaky Retry
Mediumchevron_right
terminalAwait Missing in Fire-and-Forget
Easychevron_right
terminalforEach With an Async Callback
Easychevron_right
terminalLoop Mutates the Source Array
Mediumchevron_right
terminalPermit Released Twice on Success
Mediumchevron_right
terminalRejection Escapes Several Call Hops
Hardchevron_right

Ready incidents

Playable now through the existing challenge engine.

terminalThe Flaky Retry
Mediumchevron_right
terminalThe Retry That Amplified Outages
Easychevron_right
terminalThe Event That Fired Twice
Mediumchevron_right
terminalThe Rate Limit That Counted Everyone
Mediumchevron_right
terminalThe Lock That Never Let Go
Mediumchevron_right
terminalDedupe window too short
Easychevron_right
terminalEvent id mutated by middleware
Easychevron_right
terminalDedupe cache evicts too eagerly
Mediumchevron_right
terminalAsync dedupe race
Hardchevron_right
terminalDedupe stuck on failure
Hardchevron_right
terminalAttempt Counter Reset Mid-Loop
Easychevron_right
terminalTimeout Not Cleared on Success
Easychevron_right
terminalPartial Success Discarded by Batch
Easychevron_right
terminalBackoff Overflow at High Attempts
Mediumchevron_right
terminalJitter Can Go Negative
Mediumchevron_right
terminalRetry Budget Shared Across Callers
Mediumchevron_right
terminalCircuit Half-Open Floods Requests
Mediumchevron_right
terminalDeadline Truncated Silently
Hardchevron_right
terminalRetry After Shutdown Stalls Quietly
Hardchevron_right
terminalBackoff Jitter RNG Reset Per Attempt
Hardchevron_right
terminalThe Lock That Left Too Soon
Easychevron_right
terminalLock Around the Wrong Axis
Mediumchevron_right
terminalThe Order That Stayed Open
Mediumchevron_right
terminalThe Crossed Wires
Hardchevron_right
terminalThe Retry That Charged Twice
Hardchevron_right
terminalRate-limit window never resets
Easychevron_right
terminalToken bucket refills on every request
Mediumchevron_right
terminalRate-limit bucket shared across users
Mediumchevron_right
terminalAwait Missing in Fire-and-Forget
Easychevron_right
terminalforEach With an Async Callback
Easychevron_right
terminalLoop Mutates the Source Array
Mediumchevron_right
terminalPermit Released Twice on Success
Mediumchevron_right
terminalRejection Escapes Several Call Hops
Hardchevron_right
terminalRegistry Reset Forgets Half the State
Easychevron_right
terminalSpy Counter Survives Reset
Mediumchevron_right
terminalFailover Still Routes to Primary
Mediumchevron_right
terminalDuplicate webhook processing
Mediumchevron_right

Planned Debugging 50 patterns

Visible for roadmap context only. These entries are not playable.

35Lock Not Released On Error
Planned
40Async Cleanup Race
Planned
45Rate Limiter Shared Globally
Planned
47Partial Refund Race
Planned
49Queue Consumer Drops Failures
Planned
50Worker Processes Same Job Twice
Planned
56Saga Compensation Missing
Planned
60Distributed Lock Clock Skew
Planned