# The Software Engineering Landscape (2026) > Companion to docs/learning/swe-landscape.md. One milestone per domain, each a link hub to canonical sources. Pick 2-3 milestones to go deep on; treat the rest as vocabulary. Canonical: https://learn.significanthobbies.com/curriculum/roadmaps/swe-landscape Companion to docs/learning/swe-landscape.md. One milestone per domain, each a link hub to canonical sources. Pick 2-3 milestones to go deep on; treat the rest as vocabulary. - Horizon: 12mo - Outcome: Get a working mental model of every major systems-software domain — LLMs, DBs, streaming, game engines, containers, browsers, compilers, OS, networking, distributed, build, crypto. - Tracks: System Design, Databases & Storage, AI Systems, Backend Work each milestone as a claim that needs evidence. Predict the mechanism and failure mode first, study the linked concepts, complete the drills without copying an answer, and preserve the resulting code, measurements, or design. ## Milestone 1: Prerequisites — unlock the rest of this path Concepts the later milestones depend on. Without these the planner cannot serve the rest of this roadmap. ### Concepts - [Caching](https://learn.significanthobbies.com/curriculum/concepts/caching) — Cache-aside, write-through, eviction policies. - [CDN & Edge Delivery](https://learn.significanthobbies.com/curriculum/concepts/cdn-edge-delivery) — Cache hierarchy, origin shield, and invalidation versus TTL at the edge. - [Pagination](https://learn.significanthobbies.com/curriculum/concepts/pagination) — Offset versus cursor pagination, stable ordering, and why deep pages get expensive. - [Queueing Theory](https://learn.significanthobbies.com/curriculum/concepts/queueing-theory) — Little's law and the utilisation curve — why latency explodes before a system runs out of capacity. - [Transaction Processing](https://learn.significanthobbies.com/curriculum/concepts/transaction-processing) — ACID, MVCC, isolation anomalies, locking, optimistic control, serializability, commit, and recovery. - [Isolation Levels & MVCC](https://learn.significanthobbies.com/curriculum/concepts/isolation-levels) — What each isolation level actually prevents, and how MVCC delivers snapshots without read locks. - [Retries & Circuit Breakers](https://learn.significanthobbies.com/curriculum/concepts/retries-and-circuit-breakers) — Backoff, jitter, budgets, and breakers — retrying without turning a blip into an outage. - [Web Security Basics](https://learn.significanthobbies.com/curriculum/concepts/web-security-basics) — XSS, CSRF, SQL injection, and CORS — the injection and confused-deputy bugs that keep recurring. - [Capacity Estimation](https://learn.significanthobbies.com/curriculum/concepts/capacity-estimation) — Back-of-the-envelope QPS, storage, and bandwidth maths that sizes a design before you draw it. - [Requirements Scoping](https://learn.significanthobbies.com/curriculum/concepts/requirements-scoping) — Separating functional from non-functional requirements and cutting scope to something buildable. - [LoRA & PEFT](https://learn.significanthobbies.com/curriculum/concepts/ml-lora) — Frozen base, low-rank adapters, rank/alpha. - [API Design](https://learn.significanthobbies.com/curriculum/concepts/api-design) — REST, gRPC, versioning, pagination. - [Consistent Hashing](https://learn.significanthobbies.com/curriculum/concepts/consistent-hashing) — Ring, virtual nodes, rebalancing. - [Descriptive Statistics](https://learn.significanthobbies.com/curriculum/concepts/descriptive-statistics) — Summarizing data: mean, median, variance, correlation, and when each summary lies. - [Embeddings](https://learn.significanthobbies.com/curriculum/concepts/embeddings) — Mapping text/images into dense vectors where distance encodes meaning. - [Idempotency](https://learn.significanthobbies.com/curriculum/concepts/idempotency) — Idempotency keys and dedup windows for safe retries of mutations. - [Multi-Head Attention](https://learn.significanthobbies.com/curriculum/concepts/ml-multi-head) — Parallel heads, head_dim split, output projection. - [Tokenization (LLM)](https://learn.significanthobbies.com/curriculum/concepts/ml-tokenization) — Byte-level, char-level, BPE, vocab design. - [Training & Debugging](https://learn.significanthobbies.com/curriculum/concepts/ml-training) — Init, NaNs, overfit tests, gradient checks. - [Object Modeling](https://learn.significanthobbies.com/curriculum/concepts/object-modeling) — Identifying classes, attributes, relationships. - [Probability Fundamentals](https://learn.significanthobbies.com/curriculum/concepts/probability-fundamentals) — Sample spaces, conditional probability, independence, and Bayes' rule for updating beliefs. - [Structured Outputs](https://learn.significanthobbies.com/curriculum/concepts/structured-outputs) — Forcing LLM output into a validated JSON schema. - [Checkpointing](https://learn.significanthobbies.com/curriculum/concepts/ml-checkpointing) — Weights + optimizer state, resume, dataset manifests. - [ML Math Foundations](https://learn.significanthobbies.com/curriculum/concepts/ml-math) — Vectors, matrices, dot products, matmul, shapes. - [Softmax & Cross-Entropy](https://learn.significanthobbies.com/curriculum/concepts/ml-softmax-xent) — Logits to probabilities, negative log-likelihood loss. - [Gradient Descent](https://learn.significanthobbies.com/curriculum/concepts/ml-gradient-descent) — Loss surfaces, learning rate, SGD steps. - [Language Modeling](https://learn.significanthobbies.com/curriculum/concepts/ml-language-modeling) — Next-token prediction, context windows, perplexity. - [Backpropagation](https://learn.significanthobbies.com/curriculum/concepts/ml-backprop) — Chain rule, autograd, forward/backward passes. - [Embeddings (Transformer)](https://learn.significanthobbies.com/curriculum/concepts/ml-embeddings) — Token & position embeddings, tied weights. - [AdamW Optimizer](https://learn.significanthobbies.com/curriculum/concepts/ml-adamw) — Moments, weight decay, gradient clipping. ## Milestone 2: LLMs and inference engines Transformers end-to-end, KV cache, paged attention, quantization. ### Concepts - [Self-Attention](https://learn.significanthobbies.com/curriculum/concepts/ml-self-attention) — Q/K/V, scaled dot-product, causal masking. - [Transformer Block](https://learn.significanthobbies.com/curriculum/concepts/ml-transformer-block) — Pre-LayerNorm, residuals, MLP, GELU. - [Sampling & Decoding](https://learn.significanthobbies.com/curriculum/concepts/ml-sampling) — Temperature, top-k, greedy decoding. - [RAG](https://learn.significanthobbies.com/curriculum/concepts/rag) — Retrieval-Augmented Generation: ground an LLM answer in retrieved context. - [Model Routing](https://learn.significanthobbies.com/curriculum/concepts/model-routing) — Sending each request to the cheapest model that can handle it. - [RL Alignment (GRPO & Policy Gradient)](https://learn.significanthobbies.com/curriculum/concepts/ml-rl-alignment) — Policy gradient, advantages, GRPO/CISPO, on- vs off-policy RLHF. ## Milestone 3: Databases and storage engines B-trees, LSM, WAL, MVCC, columnar — see the dedicated DB roadmap. ### Concepts - [B-Tree](https://learn.significanthobbies.com/curriculum/concepts/b-tree) — The balanced, disk-friendly tree behind most relational indexes. - [LSM Tree](https://learn.significanthobbies.com/curriculum/concepts/lsm-tree) — Log-structured merge tree: write-optimized storage via sorted runs. - [Write-Ahead Log](https://learn.significanthobbies.com/curriculum/concepts/wal) — Append-only durability log written before the data pages. - [Columnar Storage](https://learn.significanthobbies.com/curriculum/concepts/columnar-storage) — Column-oriented layout for analytics: compression and vectorized scans. ## Milestone 4: Streaming and event systems Append-only logs, partitions, watermarks, stateful stream processing. ### Concepts - [Message Queues](https://learn.significanthobbies.com/curriculum/concepts/message-queues) — Kafka, SQS, exactly-once vs at-least-once. - [Real-time Systems](https://learn.significanthobbies.com/curriculum/concepts/messaging-realtime) — WebSockets, server-sent events, presence, synchronization, ordering, reconnects, optimistic UI, and conflict handling. - [Retries & DLQ](https://learn.significanthobbies.com/curriculum/concepts/retries-dlq) — Backoff + jitter, poison messages, dead-letter queues. ## Milestone 5: Game engines and real-time graphics Fixed-step loops, ECS, render pipelines, GPU command buffers. ### Concepts - [Game/Simulation Design](https://learn.significanthobbies.com/curriculum/concepts/game-design) — Turn engines, board state, rules. - [Concurrency Design](https://learn.significanthobbies.com/curriculum/concepts/concurrency-design) — Thread-safety, locks, producer-consumer. ## Milestone 6: Containers and orchestration Linux namespaces, cgroups, OCI runtimes, Kubernetes scheduling. ### Concepts - [Distributed Infra](https://learn.significanthobbies.com/curriculum/concepts/distributed-infra) — Service discovery, orchestration. - [Load Balancing](https://learn.significanthobbies.com/curriculum/concepts/load-balancing) — L4/L7, consistent hashing, health checks. ## Milestone 7: Browsers (Chromium, Firefox, Servo) Parser, layout, JS engine, compositor, sandboxing, WebAssembly. ### Concepts - [Browser ML Runtime](https://learn.significanthobbies.com/curriculum/concepts/ml-browser-runtime) — Web Workers, WASM, OPFS, TypedArrays. - [WebGPU Compute](https://learn.significanthobbies.com/curriculum/concepts/ml-webgpu) — WGSL, compute kernels, matmul, CPU parity. ## Milestone 8: Compilers and language runtimes Lexer → parser → AST → IR → optimization → codegen; GC, JIT. ### Concepts - [State Machines](https://learn.significanthobbies.com/curriculum/concepts/state-management) — States, transitions, guards. - [Strategy Pattern](https://learn.significanthobbies.com/curriculum/concepts/strategy-pattern) — Interchangeable algorithms. ## Milestone 9: Operating systems and kernels Processes, virtual memory, schedulers, file systems, syscalls. ### Concepts - [Concurrency Design](https://learn.significanthobbies.com/curriculum/concepts/concurrency-design) — Thread-safety, locks, producer-consumer. ## Milestone 10: Networking and protocols TCP/IP, TLS, HTTP/2 and HTTP/3, QUIC, BGP. ### Concepts - [HTTP Lifecycle](https://learn.significanthobbies.com/curriculum/concepts/http-lifecycle) — DNS → TCP/TLS → request → response: status codes, headers, keep-alive. - [Load Balancing](https://learn.significanthobbies.com/curriculum/concepts/load-balancing) — L4/L7, consistent hashing, health checks. ## Milestone 11: Distributed systems Consensus, replication, 2PC, gossip, vector clocks. ### Concepts - [Consensus](https://learn.significanthobbies.com/curriculum/concepts/consensus) — Raft, Paxos, leader election. - [CAP & Consistency Models](https://learn.significanthobbies.com/curriculum/concepts/cap-theorem) — Strong/eventual/causal, PACELC. - [Distributed Infra](https://learn.significanthobbies.com/curriculum/concepts/distributed-infra) — Service discovery, orchestration. - [Sharding](https://learn.significanthobbies.com/curriculum/concepts/sharding) — Range/hash/geo partitioning. - [Replication](https://learn.significanthobbies.com/curriculum/concepts/replication) — Leader-follower, multi-leader, quorum. ## Milestone 12: Build systems and developer tooling Incremental builds, content-addressed caches, LSP, tree-sitter. ### Concepts ## Milestone 13: Cryptography (applied) Primitives, signatures, AEAD, TLS, MLS, ZKPs. ### Concepts - [Auth Systems](https://learn.significanthobbies.com/curriculum/concepts/auth-systems) — OAuth2, JWT, session, RBAC.