What is the difference between asynchronous and synchronous loggers?

• A. Asynchronous logging messages are faster (executed in a thread separate from the app), but may be lost in a crash.
• B. Synchronous logging messages are faster and never lose events.
• C. There is no difference between asynchronous and synchronous logging.
• D. Asynchronous logs require more memory but don't affect performance.

Answer: (A)

Asynchronous logging delegates the actual write operation to a separate worker thread and usually uses an in‑memory queue. The calling code can continue immediately, so logging incurs little or no visible latency and the application throughput remains high. But because messages sit in a buffer, a crash or sudden shutdown can leave some log events unwritten, meaning you might lose those buffered entries.

Synchronous logging, by contrast, writes the log entry in the same thread that issued the log call and waits for the I/O to complete. This guarantees that each log message is persisted before the call returns and preserves strict ordering, but it can slow down the application if logging is frequent or the I/O is slow.

The option notes that asynchronous logging is faster but may lose messages on a crash. That captures the key trade-off: improved performance and non-blocking behavior versus potential durability loss in failure scenarios. The other choices misstate the speed/durability or ignore the buffering aspect.