88 Topics — 14 Categories
Foundations
Core Principles
How to Approach SD
Structured thinking, top-down vs bottom-up methodology
Scalability
Horizontal vs vertical scaling, unit economics
Reliability
Failure modes, redundancy, graceful degradation
Availability
Nines (99.9→99.999%), SLA/SLO/SLI, failover
Performance
Latency vs throughput, P50/P95/P99 percentiles
CAP Theorem
Why "pick 2 of 3" is misleading, PACELC
ACID vs BASE
Strong vs eventual consistency trade-offs
Estimation
Traffic, storage, bandwidth, QPS calculations
Networking
Internet Basics
TCP/IP stack, what happens when you type a URL
DNS
Hierarchical resolution, GeoDNS, record types
TCP & UDP
Handshakes, congestion control, when to use each
HTTP Evolution
HTTP/1.1 → 2 → 3, QUIC, multiplexing
REST API Design
Resources, methods, status codes, versioning
Webhooks
Push vs poll, HMAC, retry, dead letter queues
Real-time
WebSockets, SSE, long polling, scaling
Proxies
Forward, reverse, Nginx, HAProxy, Envoy
Databases
Relational DBs
ACID, indexing (B+ tree), normalization
Isolation & Locking
4 levels, SKIP LOCKED, MVCC, deadlocks
Schema Design
ER diagrams, soft deletes, migrations
SQL Tuning
EXPLAIN plans, N+1, connection pooling
Scaling DBs
Replication, read replicas, failover, PgBouncer
Sharding
Hash/range/directory, consistent hashing, Vitess
DB Internals
B+ tree, LSM tree, pages, buffer pool, WAL
WAL (Write-Ahead Log)
How databases survive crashes; LSN, fsync, group commit
NoSQL & DB Selection
MongoDB
Document store, BSON, replica sets, sharding
Redis Deep Dive
In-memory data structures, persistence, clustering
Cassandra
Wide-column, LWT, tunable consistency, gossip
Neo4j
Graph database, Cypher, index-free adjacency
Elasticsearch
Inverted index, shards, search relevance
Time-Series DBs
InfluxDB, TimescaleDB, Prometheus internals
NewSQL
Spanner, CockroachDB, TiDB, distributed SQL
Picking the Right DB
Decision framework: relational vs NoSQL vs NewSQL
Polyglot Persistence
Multi-DB architectures, CDC-driven sync
Caching
Caching Strategies
Cache-aside, write-through, write-behind, refresh-ahead
Eviction Internals
LRU, LFU, ARC, TinyLFU — the data structures
Cache Invalidation
TTL, purge, write-through, CDC; surrogate keys
CDN
Anycast, GeoDNS, edge compute, cache keys
Caching Levels
6-layer hierarchy: CPU → page cache → app → distributed → DB buffer pool → CDN
Messaging
Message Queues
RabbitMQ, SQS, delivery guarantees, DLQs
Kafka Deep Dive
Distributed log, partitions, ISR, KRaft, EOS
Pub/Sub
Publisher-subscriber model, topics, fan-out
Async Patterns
Promises, event loops, async/await, reactive
Stream Processing
Flink, Kafka Streams, watermarks, windowing
Real-Time Analytics
Druid, Pinot, ClickHouse — sub-second OLAP
Distributed Systems
Consistency Models
Strong, eventual, causal, linearizability
Consensus
Raft, Paxos, how nodes agree despite failures
Clocks & Ordering
Lamport, vector clocks, TrueTime
Consistent Hashing
Ring, vnodes, data migration, jump hashing
Load Balancing & Resilience
Load Balancers
L4 vs L7, algorithms, health checks, DNS-based
API Gateway
Auth, rate limiting, routing, aggregation
Rate Limiting
Token bucket, sliding window, library vs service
Circuit Breaker
3-state model, bulkhead, exponential backoff
Idempotency
Keys, exactly-once patterns, Stripe's approach
Storage & Data
S3 / Blob Storage
Signed URLs, multipart, erasure coding, 11 nines
Distributed FS
GFS, HDFS, chunk storage, fault tolerance
Tiered Storage
Hot/warm/cold/glacier, cost optimization
Batch Processing
MapReduce, Spark, data locality, lineage
Serialization
Serialization Formats
JSON, Protobuf, Avro, MessagePack — when to pick each
Compression
gzip, brotli, zstd — bandwidth-vs-CPU trade-offs
Architecture Patterns
Monolith vs Micro
Trade-offs, decomposition, database per service
Event-Driven
Event sourcing, CQRS, saga, outbox pattern
Service Mesh
Istio, sidecar proxies, Consul, etcd
Communication
sync (REST, gRPC) vs async (events), BFF
Security
Auth
OAuth 2.0, JWT, SSO, RBAC/ABAC, session management
TLS / Encryption
Handshake, certificates, mTLS, KMS
API Security
CORS, CSRF, DDoS, OWASP top 10
Zero Trust
Service-to-service auth, VPC, segmentation
Observability
Logging
Structured logging, ELK, correlation IDs
Metrics
Prometheus, Grafana, RED/USE methods
Tracing
Jaeger, OpenTelemetry, trace/span propagation
Alerting
On-call, runbooks, alert fatigue, postmortems
Infrastructure
Containers & K8s
Docker, pods, services, ingress, scaling
CI/CD
Build, test, deploy, artifacts, GitOps
Deployment
Blue-green, canary, rolling, feature flags
Serverless
Lambda, cold starts, concurrency, event-driven
IaC
Terraform, CloudFormation, immutable infrastructure