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Hectal

Bloom filters · from first bit to FAANG-level design

"Definitely not" or "maybe".
Know the maths, the variants, and what breaks.

Bloom filters taught as engineering, not trivia: the false-positive maths and sizing, hashing, a thread-safe versioned implementation, counting, scalable, blocked, cuckoo, quotient, xor and ribbon variants, LSM engines and CDNs, RedisBloom cache-penetration protection, keeping filters fresh with Kafka and CDC, rebuilds, distributed and multi-region filters, observability and security. Every topic works through a real interview problem and the ways it breaks in production, ending with FAANG-style designs and a 50-question revision bank.

Start from zero The full roadmap
Phases
12
Topics
48
Hours
6
Diagrams
22
Exercises
178

By the end you can

What this course makes you able to do

  • Explain false positives and false negatives precisely, and why a correct filter never returns a false negative
  • Size any filter live: derive the FPR formula, compute m and k, and predict saturation past capacity
  • Implement a thread-safe, serialisable, versioned Bloom filter with good hashing
  • Choose between Bloom, counting, scalable, blocked, cuckoo, quotient, xor and ribbon filters, and justify it
  • Design cache penetration protection with a filter, Redis and a database, kept fresh through Kafka or CDC with safe rebuilds
  • Answer staff-level design questions with the full reasoning chain: requirement → error budget → sizing → variant → freshness → failure → trade-offs

Beginner → Advanced

The curriculum, by level

Beginner
  1. 0Probabilistic Foundations3 topics · ~24 min
  2. 1The Mathematics4 topics · ~32 min
Intermediate
  1. 2Hash Functions3 topics · ~22 min
  2. 3Building a Production Filter4 topics · ~34 min
  3. 4Variants and Alternatives6 topics · ~49 min
  4. 5Storage Engines and the Edge3 topics · ~23 min
  5. 6Bloom Filters with Redis and Databases4 topics · ~32 min
Advanced
  1. 7Consistency and Filter Lifecycle4 topics · ~34 min
  2. 8Distributed Bloom Filters3 topics · ~25 min
  3. 9Operating Bloom Filters4 topics · ~32 min
  4. 10System Design with Bloom Filters5 topics · ~41 min
  5. 11Interview Revision5 topics · ~33 min

Where should I start?

Pick a path for your goal

Fundamentals (0–2 years)

You've heard of Bloom filters and want to truly understand them.

  1. 10 · Probabilistic Foundations
  2. 21 · The Mathematics
  3. 32 · Hash Functions
  4. 43 · Building a Production Filter

Then Phase 6 to use one in front of Redis and a database.

Interview-ready (2–4 years)

You need to size, choose and design filters in interviews.

  1. 11 · The Mathematics
  2. 24 · Variants and Alternatives
  3. 35 · Storage Engines and the Edge
  4. 46 · Bloom Filters with Redis and Databases
  5. 57 · Consistency and Filter Lifecycle
  6. 610 · System Design with Bloom Filters

Finish with the Phase 11 question bank.

Senior / Staff

You own filters in production or lead system design rounds.

  1. 17 · Consistency and Filter Lifecycle
  2. 28 · Distributed Bloom Filters
  3. 39 · Operating Bloom Filters
  4. 410 · System Design with Bloom Filters
  5. 511 · Interview Revision