TopicsLow-level design
Low-level design
OOP and SOLID class design for machine-coding LLD: interfaces, invariants, in-memory state, and concurrency you can implement and test.
Common tags: lld, ood, machine-coding, concurrency
- Low-level design
Rate Limiter - Token Bucket + Sliding Window Solution & Tests
Cluster · LLM Gateway Rate Limiter
Runnable TokenBucket, SlidingWindowLog, and GatewayLimiter, with a fake clock and an 80-thread burst flood.
Open study →- lld
- rate-limiting
- llm
- token-bucket
- sliding-window
- interview
- machine-coding
- ood
- Low-level design
Rate Limiter - Concurrency, Retry-After & Composition
Cluster · LLM Gateway Rate Limiter
Why one RLock around the composed check still counts an RPM event when the burst denies, how retry_after_ms is computed, and how this round maps onto Redis Lua.
Open study →- lld
- rate-limiting
- llm
- token-bucket
- sliding-window
- interview
- machine-coding
- ood
- Low-level design
Rate Limiter for an LLM Gateway - LLD Spec & Concepts
Cluster · LLM Gateway Rate Limiter
Machine-coding LLD for an in-process LLM gateway limiter: a per-tenant token bucket, an exact sliding-window log, and a composed decision with remaining and retry_after_ms.
Open study →- lld
- rate-limiting
- llm
- token-bucket
- sliding-window
- interview
- machine-coding
- ood
- Low-level design
Feature Flag Service LLD - Targeting, Sticky Buckets & Kill Switches
Cluster · Feature Flag Service
Provisional machine-coding LLD for an in-memory flag service: kill switch, disabled, segment gate, then a sticky SHA-256 percentage.
Open study →- lld
- feature-flags
- bucketing
- kill-switch
- interview
- machine-coding
- ood
- Low-level design
Comments and Replies LLD - Spec, Design Steps & Concepts
Cluster · Comments and Replies
Two-level in-memory comments/replies LLD: spec, structure choices, independent IDs, order, snapshots, concepts.
Open study →- lld
- comments
- replies
- concurrency
- interview
- machine-coding
- ood
- Low-level design
ArchiveSweep (File Deduplication) LLD - Spec, Pipeline & Concepts
Cluster · ArchiveSweep
Machine-coding LLD: recursively scan a directory tree, skip symlinks, collapse hard links to one inode, then find byte-identical duplicate groups with a staged pipeline (size -> sample prefix -> streaming SHA-256 -> byte verify).
Open study →- lld
- archivesweep
- dedup
- hashing
- concurrency
- interview
- machine-coding
- ood
- Low-level design
Feature Flag Service - Sticky Bucket + Kill Switch Solution & Tests
Cluster · Feature Flag Service
Runnable FlagStore with upsert, sticky SHA-256 bucketing, segment gates, kill-switch precedence, and a concurrent upsert/evaluate test.
Open study →- lld
- feature-flags
- bucketing
- kill-switch
- interview
- machine-coding
- ood
- Low-level design
Feature Flag Service - Evaluation Order & Concurrency
Cluster · Feature Flag Service
Why the kill switch short-circuits before the percentage, why get copies the flag, and how this round connects to progressive delivery.
Open study →- lld
- feature-flags
- bucketing
- kill-switch
- interview
- machine-coding
- ood
- Low-level design
Comments and Replies - In-Memory Solution, Ordering & Tests
Cluster · Comments and Replies
Full CommentService Python+TS sketch with tests for order, validation, isolation, independent IDs, concurrency, snapshots.
Open study →- lld
- comments
- replies
- concurrency
- interview
- machine-coding
- ood
- Low-level design
Comments and Replies - Concurrent IDs, Snapshots & Post Isolation
Cluster · Comments and Replies
Concurrent ID allocation, defensive snapshots, post isolation, lock granularity decision chart, follow-ups.
Open study →- lld
- comments
- replies
- concurrency
- interview
- machine-coding
- ood
- Low-level design
ArchiveSweep - Streaming SHA Solution & Tests
Cluster · ArchiveSweep
Full runnable stdlib implementation: archive_sweep(root, workers) with scan, sample, stream hash, byte verify, ThreadPoolExecutor, and unittest coverage for duplicates, near-misses, symlinks, hard links, and empty files.
Open study →- lld
- archivesweep
- dedup
- hashing
- concurrency
- interview
- machine-coding
- ood
- Low-level design
ArchiveSweep - Concurrency, Symlinks & Hardlink Edge Cases
Cluster · ArchiveSweep
Which stages parallelize safely, how to aggregate errors without losing groups, symlink policy, hardlink reclaim math, and how to explain the design without overselling hash equality.
Open study →- lld
- archivesweep
- dedup
- hashing
- concurrency
- interview
- machine-coding
- ood