Built a single-node log service that speaks Kafka. Handles sparse offsets and never loses writes, all while keeping things monotonic. Map-based storage made this surprisingly clean.
Map for offset -> message (sparse offsets for free)
Thread-safe ops with RWMutex
Monotonic offset counter separate from storage
No assumptions about gaps or contiguity
Monotonic Offsets: nextOffset counter never goes backwards
No Lost Writes: Map storage means gaps are fine but nothing disappears
Thread Safety: RWMutex keeps concurrent ops clean
Simple Polling: Sequential scan from requested offset just works
Pros:
Natural sparse offset handling
Clean concurrent access patterns
Simple offset management
Easy to reason about safety properties
Cons:
Unbounded memory usage (but spec doesn't care)
Sequential scans for polls
No cleanup mechanism
Full copy on response building
Can go fancy with skip lists or cleanup strategies, but keeping it simple with maps just worked. Next, multi-node!
