Concept Map: all 111, mapped and prioritised

Tiers

# Concept One-line meaning Module Tier
1 Rate Limiting Cap requests per user/IP/key per window M05 Now
2 Caching Store computed results to avoid redoing work M09 Growth
3 Load Balancing Spread traffic across several servers M09 Scale
4 Reverse Proxies A server in front of your app (TLS, routing, buffering) M09 Growth
5 API Gateways One front door for auth, quotas and routing to many services M09 Scale
6 CI/CD Every change tested and deployed automatically M11 Now
7 Docker Package app + dependencies into a reproducible image M11 Growth
8 Kubernetes Orchestrate many containers across many machines M11 Scale
9 Service Discovery Services find each other's addresses dynamically M11 Scale
10 Circuit Breakers Stop calling a failing dependency for a while M07 Growth
11 Timeouts Never wait forever on anything M07 Now
12 Retries Try again on transient failure M07 Now
13 Exponential Backoff Wait longer between each retry, with jitter M07 Now
14 Idempotency Doing it twice has the same effect as once M04 Now
15 Message Queues Hand work to a worker via a durable buffer M08 Growth
16 Pub/Sub One event, many independent subscribers M08 Growth
17 Event-Driven Architecture Services react to facts that happened M08 Scale
18 Distributed Transactions One logical change across several systems M08 Scale
19 Saga Pattern Multi-step workflow with compensating undo steps M08 Growth
20 Dead Letter Queues Park messages that keep failing for inspection M07 Growth
21 Cron Jobs Scheduled work M08 Now
22 WebSockets Two-way persistent connection M08 Growth
23 Long Polling Hold a request open until data arrives M08 Scale
24 Server-Sent Events One-way server push stream (LLM streaming) M08 Growth
25 Database Indexing Data structure that makes lookups fast M03 Now
26 Query Optimization Reading EXPLAIN plans and fixing slow SQL M03 Growth
27 N+1 Queries One query per row inside a loop M03 Now
28 Connection Pooling Reuse DB connections instead of opening new ones M03 Now
29 Read Replicas Copies of the DB that serve reads M09 Scale
30 Sharding Split data across many databases by key M09 Scale
31 Partitioning Split one big table into parts (often by time) M09 Growth
32 Replication Keep copies of data on multiple nodes M10 Growth
33 Leader Election Nodes agree on who is in charge M10 Scale
34 CAP Theorem During a partition, choose consistency or availability M10 Growth
35 Eventual Consistency Copies agree eventually, not instantly M10 Growth
36 Optimistic Locking Detect conflicting writes with a version number M03 Now
37 Pessimistic Locking Lock the row before changing it M03 Growth
38 Distributed Locks A lock shared across machines M10 Scale
39 Race Conditions Outcome depends on timing of concurrent actions M10 Now
40 Deadlocks Two actors each waiting on the other forever M10 Growth
41 Memory Leaks Memory that is never released M10 Growth
42 Garbage Collection Runtime reclaiming unused memory (and its pauses) M10 Scale
43 Thread Safety Code correct when run concurrently M10 Growth
44 Backpressure Slow producers down when consumers cannot keep up M07 Growth
45 Autoscaling Add or remove capacity automatically M09 Scale
46 Horizontal Scaling More machines M09 Scale
47 Vertical Scaling Bigger machine M09 Growth
48 CDN Serve static content from near the user M09 Now
49 Edge Caching Cache dynamic responses at the CDN M09 Growth
50 Cache Invalidation Knowing when cached data is stale M09 Growth
51 Feature Flags Turn code paths on/off without deploying M11 Growth
52 Blue-Green Deployment Two environments, switch traffic instantly M11 Scale
53 Canary Releases Release to a small % first M11 Scale
54 Rolling Deployments Replace instances gradually M11 Growth
55 Rollbacks Return to the last good version fast M11 Now
56 Health Checks Endpoint saying "I am OK" M12 Now
57 Liveness & Readiness Probes "Am I alive?" vs "Can I take traffic?" M12 Growth
58 Monitoring Watching known signals M12 Now
59 Logging Structured records of events M12 Now
60 Distributed Tracing Following one request across services M12 Growth
61 Metrics Numeric time series (rate, errors, duration) M12 Growth
62 Alerts Paging a human when users are hurting M12 Now
63 SLOs Target reliability, e.g. 99.9% of requests OK M12 Growth
64 SLIs The measured indicator behind an SLO M12 Growth
65 Error Budgets Allowed unreliability; spend it on shipping M12 Scale
66 Observability Asking new questions of a running system M12 Growth
67 Secrets Management Keys never in code, frontend or logs M05 Now
68 IAM Who/what may do which action on which resource M05 Now
69 OAuth Delegated authorization standard M05 Now
70 JWT Rotation Short-lived tokens, rotated signing keys M05 Growth
71 TLS Encrypted, authenticated connections M02 Now
72 Encryption at Rest Data encrypted on disk/backups M05 Now
73 Encryption in Transit Data encrypted on the wire, internal too M02 Now
74 WAF Filter malicious HTTP traffic M05 Growth
75 DDoS Protection Absorb floods of traffic M05 Growth
76 CORS Browser rule for which origins may call your API M05 Now
77 CSRF Tricking a logged-in browser into acting M05 Now
78 SQL Injection Input executed as SQL M05 Now
79 XSS Input executed as script in other users' browsers M05 Now
80 SSRF Server tricked into fetching internal URLs M05 Now
81 Database Migrations Versioned, scripted schema changes M03 Now
82 Schema Versioning Old and new code coexist with the schema M03 Growth
83 Disaster Recovery Plan + RPO/RTO for losing a region or provider M13 Growth
84 Backups Copies you have proven you can restore M13 Now
85 Failover Switching to a standby automatically M13 Scale
86 Multi-Region Deployment Running in several geographic regions M13 Scale
87 Chaos Engineering Injecting failure on purpose to learn M13 Scale
88 Cost Optimization Spend matched to value; spend caps M09 Now
89 Cold Starts Latency when a serverless function wakes M09 Growth
90 Serverless Limits Timeouts, memory, payload, concurrency caps M09 Now
91 Latency Time for one request M02 Now
92 Throughput Requests per second the system handles M02 Growth
93 P99 Latency The slowest 1% of requests M02 Growth
94 Tail Latency Why the slow tail dominates user experience M02 Growth
95 Network Partitions Parts of the system cannot talk M10 Scale
96 Clock Skew Machines disagree about the time M10 Scale
97 DNS Names to addresses; TTLs; propagation M02 Now
98 TCP vs UDP Reliable ordered stream vs fast datagrams M02 Scale
99 HTTP/2 & HTTP/3 Multiplexing; QUIC over UDP M02 Scale
100 gRPC Typed binary RPC over HTTP/2 M04 Scale
101 Webhooks Server-to-server callbacks; verify signatures M08 Now
102 API Versioning Change APIs without breaking clients M04 Growth
103 Semantic Versioning MAJOR.MINOR.PATCH meaning M04 Growth
104 Infrastructure as Code Infra defined in versioned files M11 Growth
105 Terraform The most common IaC tool (OpenTofu fork) M11 Scale
106 Helm Charts Packaged Kubernetes apps M11 Scale
107 Build Caching Reuse build outputs to speed CI M11 Scale
108 Dependency Hell Conflicting, vulnerable or hallucinated packages M11 Now
109 Production Incidents Something is broken for users right now M13 Now
110 On-Call Who responds, how fast, with what runbook M13 Growth
111 Postmortems Blameless learning after incidents M13 Growth

Count by tier

What the poster is missing (taught in this school)

Concept Module Tier
Row-Level Security / tenant isolation M05 Now
Software supply chain (SBOM, pinning, SLSA, slopsquatting) M11 Now
Prompt injection and agent goal hijack M06 Now
Least agency + human approval on irreversible actions M06 Now
LLM cost controls and spend caps M06, M09 Now
Audit trails M14 Now
Data protection law (PDPA, GDPR) M14 Now
Testing pyramid and evals M01, M06 Now
Mishandling of exceptional conditions (OWASP A10:2025) M07 Now
AI governance (IMDA MGF for Agentic AI, EU AI Act) M14 Growth
Accessibility (WCAG) M01 Growth
Multi-tenancy design M03 Growth