Implement a Leaky-Bucket Rate Limiter with Tests and Distributed Design

Context and Assumptions

• Implement in a general-purpose language; the reference solution uses Python 3 for clarity and unit tests.
• Leaky bucket semantics: a fixed drain rate r units/sec, a finite capacity b units. Each request consumes 1 unit unless specified otherwise. The bucket "leaks" continuously at rate r.
• The limiter should support:
  1. try_acquire(n=1) that returns whether a request of size n is allowed now and, if not, the wait time until it would be allowed.
  2. Unit tests for steady-state, burst, and boundary conditions.
  3. Discussion of concurrency safety (multi-thread/process) and distributed extension (e.g., Redis) with consistency & failure-mode considerations.

Task

1. Implement a leaky-bucket rate limiter enforcing a maximum average request rate with a fixed drain rate.
2. Write unit tests to validate:
   • Steady-state behavior at/under the configured rate.
   • Burst behavior up to capacity.
   • Boundary/edge conditions (precision, zero/near-zero time deltas, exact thresholds).
3. Explain how to make the limiter safe under concurrency.
4. Propose a design to extend it in a distributed setting (e.g., Redis), including consistency and failure-mode considerations.