## Round 1 - Coding / OOD ## Problem Design a `Trailer` data structure — a fixed-capacity circular buffer that keeps only the last `N` items added. Support adding items, iterating in insertion order, and querying the current count. ```python class Trailer: def __init__(self, capacity: int): ... def add(self, item) -> None: # oldest item is evicted when capacity is exceeded ... def __iter__(self): # yields items oldest to newest ... def __len__(self) -> int: ... def latest(self) -> any: # returns the most recently added item ... ``` ## Example ``` t = Trailer(3) t.add("a"); t.add("b"); t.add("c") list(t) -> ["a", "b", "c"] t.add("d") list(t) -> ["b", "c", "d"] # "a" evicted len(t) -> 3 t.latest() -> "d" ``` ## Follow-ups 1. What is the time complexity of `add` and iteration in your implementation? 2. How would you make this thread-safe for concurrent producers and consumers? 3. How would you extend this to support a `window_sum()` or `window_average()` that operates on numeric items in O(1)? 4. How does this differ from Python's `collections.deque(maxlen=N)` — what does `deque` give you for free?

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Trailer: Implement a Fixed-Size Trailing Buffer That Captures the Last N Events

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Round 1 - Coding / OOD Problem Design a Trailer data structure — a fixed-capacity circular buffer that keeps only the last N items added. Support adding items, iterating in insertion order, and querying the current count. Example Follow-ups What is the time complexity of add and iteration in your implementation? How would you make this thread-safe for concurrent producers and consumers? How would you extend this to support a window_sum() or window_average() that operates on numeric items in O(1)…

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This is a reported interview question from a samsara interview during the phone round.

It covers the following topics: Coding, Queue, Ood, Phone .

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Trailer: Implement a Fixed-Size Trailing Buffer That Captures the Last N Events

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