Building Blocks

The parts most systems are built from: DNS, load balancers, APIs, caches, databases, queues, and the stores behind search and maps. 6 modules, about 6 hours of reading. Every lesson ends in something to do.

Networking

Domain Name System (DNS)How a name becomes an address, why caching makes it fast, and how TTL decides your failover speed.Beginner16 min
Transport Protocols: TCP, UDP, QUICWhat happens when a packet is lost — TCP's guarantee and its cost, why real-time systems prefer loss to delay, and what QUIC changed.Intermediate18 min
Load BalancingThe algorithms, health checks, L4 versus L7, and why the load balancer itself must not be a single point of failure.Beginner17 min
Proxy vs. Reverse ProxyWhich side the intermediary protects, what each is actually used for, and how a reverse proxy differs from a load balancer.Beginner16 min

APIs

API Paradigms: REST vs GraphQL vs gRPCREST, GraphQL and gRPC — who decides the shape of the response, what each costs you, and why the answer differs per connection.Intermediate17 min
API GatewayOne front door for many services, what belongs in it, and the trap of letting it become a monolith.Intermediate16 min
Rate LimitingWhere to enforce limits in a distributed system, sharing counters across nodes, and shedding load before it hurts.Intermediate20 min

Caching and Delivery

Content Delivery Network (CDN)Beating the speed of light by moving content closer, plus cache keys, invalidation and the thundering herd.Beginner20 min
CachingWhere to put a cache, the write strategies, eviction policies, and the three failure modes that take systems down.Beginner18 min

Databases

Database Basics: SQL vs NoSQLWhat ACID actually guarantees, the four NoSQL families, and why "NoSQL scales better" is the wrong reason to choose.Beginner17 min
Database ReplicationRead replicas, sync versus async, replication lag and the read-your-own-writes bug it causes.Intermediate20 min
Data Partitioning (Sharding)Splitting data across machines, choosing a shard key, hot spots, and everything sharding makes harder.Intermediate18 min
Consistent HashingWhy modulo hashing collapses when you add a server, how the ring fixes it, and what virtual nodes are for.Advanced17 min

Messaging and Streams

Message QueuesDecoupling with async work, delivery guarantees, queues versus logs, and why dead letter queues matter.Intermediate21 min
Batch vs Stream ProcessingBounded input versus input that never ends — windows, the event-time problem, and what replaced the lambda architecture.Advanced18 min

Specialised Systems

Bloom Filters & Probabilistic StructuresTrading a little accuracy for a lot of memory — how the bits work, how to size one, and why you cannot delete from it.Advanced20 min
Distributed File Systems (DFS)Chunking huge files across machines, why the metadata node is the bottleneck, and replication versus erasure coding.Intermediate17 min
Search Systems (Elasticsearch)Inverted indexes, why LIKE queries cannot scale, relevance scoring, and keeping a search index in sync.Intermediate17 min
Spatial Indexing (QuadTrees & GeoHashing)Collapsing two dimensions into one ordered key — geohashes, quadtrees, the border problem, and what production systems actually run.Advanced19 min
Unique ID Generators (Snowflake)Generating sortable unique ids without a central bottleneck — UUIDs, ticket servers, Snowflake, and the clock problem it inherits.Advanced19 min

Networking

Domain Name System (DNS)How a name becomes an address, why caching makes it fast, and how TTL decides your failover speed.Beginner16 min

Transport Protocols: TCP, UDP, QUICWhat happens when a packet is lost — TCP's guarantee and its cost, why real-time systems prefer loss to delay, and what QUIC changed.Intermediate18 min

Load BalancingThe algorithms, health checks, L4 versus L7, and why the load balancer itself must not be a single point of failure.Beginner17 min

Proxy vs. Reverse ProxyWhich side the intermediary protects, what each is actually used for, and how a reverse proxy differs from a load balancer.Beginner16 min

APIs

API Paradigms: REST vs GraphQL vs gRPCREST, GraphQL and gRPC — who decides the shape of the response, what each costs you, and why the answer differs per connection.Intermediate17 min

API GatewayOne front door for many services, what belongs in it, and the trap of letting it become a monolith.Intermediate16 min

Rate LimitingWhere to enforce limits in a distributed system, sharing counters across nodes, and shedding load before it hurts.Intermediate20 min

Databases

Database Basics: SQL vs NoSQLWhat ACID actually guarantees, the four NoSQL families, and why "NoSQL scales better" is the wrong reason to choose.Beginner17 min

Database ReplicationRead replicas, sync versus async, replication lag and the read-your-own-writes bug it causes.Intermediate20 min

Data Partitioning (Sharding)Splitting data across machines, choosing a shard key, hot spots, and everything sharding makes harder.Intermediate18 min

Consistent HashingWhy modulo hashing collapses when you add a server, how the ring fixes it, and what virtual nodes are for.Advanced17 min

Specialised Systems

Bloom Filters & Probabilistic StructuresTrading a little accuracy for a lot of memory — how the bits work, how to size one, and why you cannot delete from it.Advanced20 min

Distributed File Systems (DFS)Chunking huge files across machines, why the metadata node is the bottleneck, and replication versus erasure coding.Intermediate17 min

Search Systems (Elasticsearch)Inverted indexes, why LIKE queries cannot scale, relevance scoring, and keeping a search index in sync.Intermediate17 min

Spatial Indexing (QuadTrees & GeoHashing)Collapsing two dimensions into one ordered key — geohashes, quadtrees, the border problem, and what production systems actually run.Advanced19 min

Unique ID Generators (Snowflake)Generating sortable unique ids without a central bottleneck — UUIDs, ticket servers, Snowflake, and the clock problem it inherits.Advanced19 min

Networking

APIs

Caching and Delivery

Databases

Messaging and Streams

Specialised Systems

Networking

APIs

Caching and Delivery

Databases

Messaging and Streams

Specialised Systems

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