Server Side Asynchronous Programming Questions

Asynchronous and concurrent programming as applied to backend systems, including event loop models, thread pools, futures and promises, asynchronous I O, streaming, and reactive frameworks. Covers Node dot js event loop and streaming APIs, Java threading models and reactive libraries such as Project Reactor or RxJava, Python asyncio and multiprocessing versus multithreading trade offs, handling blocking operations, backpressure and flow control, and patterns to structure scalable non blocking servers. Candidates should demonstrate the ability to reason about throughput, latency, resource contention, and appropriate concurrency models for server workloads.

HardTechnical

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Design a Java-based reactive event processing pipeline using Project Reactor to consume events from Kafka, enrich with DB lookups, apply business rules, and write to downstream services. Constraints: end-to-end latency < 500ms (95th), maintain at-least-once delivery with idempotency, support backpressure, and degrade gracefully under load. Describe Schedulers, parallelization strategy, batching, and testing approaches.

MediumTechnical

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In Go, implement a worker pool that processes jobs concurrently with a configurable maxWorkers and a bounded job queue of size N. Requirements: support context cancellation, graceful shutdown where in-flight jobs finish (or are cancelled by context), and expose metrics for queue length and active workers. Provide function signatures and outline how you'd test for race conditions and correct shutdown.

MediumTechnical

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As an SRE, you need to choose between an async single-threaded model (e.g., Node.js, Python asyncio) and a multi-threaded model for a new high-throughput HTTP service. Describe the trade-offs in terms of latency, throughput, memory usage, CPU utilization, handling blocking syscalls, debugging complexity, and ecosystem maturity. What criteria would cause you to pick one model over the other?

MediumTechnical

0 practiced

Implement a 'single-flight' cache loader in Python using asyncio so that concurrent coroutines requesting the same missing key cause only one fetcher coroutine to run; others await the same result. Provide signatures: async def get(key) -> value and async def _fetch(key) -> value. Ensure exceptions, cancellations, and TTLs are handled correctly to avoid stuck waiters.

MediumTechnical

0 practiced

In Node.js (JavaScript), implement a Transform stream class UppercaseStream that converts incoming Buffer chunks to uppercase strings and respects backpressure. Requirements: support objectMode=false, correctly handle multibyte UTF-8 boundaries across chunks, and demonstrate piping from fs.createReadStream through your transform to fs.createWriteStream. Explain how highWaterMark affects memory and backpressure.

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