All System Design Tools

CrackingWalnuts offers 24 free interactive system design tools for engineers. Use these calculators and visualizers to build intuition for distributed systems concepts, prepare for system design interviews, and estimate capacity requirements.

• Back-of-Envelope Calculator

  Estimate QPS, storage, bandwidth from DAU and request patterns.

• SLA / Uptime Calculator

  Convert nines to downtime. Compound SLA for dependent services.

• Data Transfer Time Calculator

  Transfer time from 1 MB to 1 PB across common link speeds.

• Latency Numbers Every Engineer Should Know

  Interactive latency reference chart from L1 cache to cross-continent network calls.

• Database Selector Quiz

  Answer workload questions, get a database recommendation.

• Throughput & Capacity Unit Converter

  Convert Mbps, MB/s, QPS, storage units, and time durations.

• Consistent Hashing Visualizer

  Hash ring with key-to-node mapping. Add/remove nodes live.

• Rate Limiter Algorithm Visualizer

  Token Bucket vs Fixed Window vs Sliding Window side-by-side.

• Bloom Filter Visualizer

  Membership testing with false positive demonstration.

• LRU / LFU / FIFO Cache Visualizer

  Step through operations, watch evictions, compare hit rates.

• Quorum & Replication Visualizer

  Configure N, W, R. Simulate failures, test consistency.

• Leader Election Visualizer

  Bully vs Ring vs Raft. Trigger elections, simulate failures.

• Circuit Breaker Visualizer

  Closed-Open-Half-Open state machine. Send requests, watch state transitions.

• Database Sharding Visualizer

  Hash vs Range partitioning. Detect hotspots, analyze distribution.

• Message Queue Patterns Visualizer

  Pub/Sub vs Point-to-Point vs Consumer Groups. Simulate message delivery.

• Load Balancer Simulator

  Round Robin vs Weighted vs Least Connections vs IP Hash. Kill servers mid-stream.

• CAP Theorem Playground

  Partition the network, toggle CP vs AP, watch consistency and availability trade off.

• Gossip Protocol Visualizer

  Watch information spread through a cluster tick by tick. Adjust fanout, kill nodes.

• B-Tree / LSM-Tree Visualizer

  Insert, search, split, compact. Compare read-optimized vs write-optimized structures.

• Distributed Transaction Visualizer

  Two-Phase Commit vs Saga. Inject failures, watch abort and compensate flows.

• Retry & Backoff Playground

  Exponential backoff with jitter. Thundering herd demo shows why jitter matters.

• Merkle Tree Visualizer

  Edit data blocks, watch hashes propagate. Compare trees with log(n) verification.

• Connection Pool Visualizer

  Borrow, use, return connections. Leak them and watch the pool drain.

• Capacity Planning Calculator

  Project storage, QPS, bandwidth over time. Know when to shard or go multi-region.

• LLM Cost Calculator

  Calculate LLM inference cost by task type, model tier, and volume. Compare API vs self-hosted.

• GPU Fleet Sizing Calculator

  Size a self-hosted GPU fleet from model size, quantization, and QPS targets.

• Vector DB Sizing Calculator

  Calculate vector database storage, HNSW overhead, and embedding costs for RAG.