docs: add interview study plan for finance/HFT roles

Covers target firms, three study tracks (LeetCode, low-level systems,
system design), a 4-phase 12-week timeline, weekly rhythm, and resources.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

org/study_plan.org

@@ -0,0 +1,145 @@
+#+title: Interview Study Plan — Finance / HFT / Systems
+#+date: 2026-04-22
+
+* Target Firms
+** HFT / Prop Trading
+- Jane Street
+- Citadel Securities
+- Virtu Financial
+- Jump Trading
+- Optiver
+- IMC
+- Susquehanna (SIG)
+- DRW
+- Flow Traders
+- Hudson River Trading
+
+** Quant Hedge Funds
+- Two Sigma
+- DE Shaw
+- Renaissance Technologies
+- AQR
+- Millennium Management
+
+** Crypto Exchanges
+- Coinbase
+- Binance
+- Kraken
+- OKX
+
+** Banks (Trading Desks / Strats)
+- Goldman Sachs
+- Morgan Stanley
+- JP Morgan
+
+** Fintech Infrastructure
+- Broadridge
+- ION Group
+- Refinitiv / LSEG
+
+* Study Tracks
+** Track 1: LeetCode / Algorithms
+- Arrays, hash maps, linked lists, stacks, queues
+- Binary search, two pointers, sliding window
+- Trees, graphs, DFS/BFS
+- Sorting, heaps
+- Dynamic programming (easy → medium)
+- Math and probability puzzles (especially for Jane Street, Optiver)
+
+** Track 2: Low-Level Systems
+*** OS & Kernel
+- Process vs thread, scheduling, context switching
+- Memory management: virtual memory, paging, TLB
+- System calls, interrupts
+- CPU caching: L1/L2/L3, cache lines, false sharing
+- NUMA architecture
+- CPU pinning / thread affinity
+
+*** Networking
+- TCP vs UDP — congestion control, reliability, ordering
+- KCP — low-latency UDP protocol
+- Kernel bypass: DPDK, RDMA
+- UDP multicast (common in market data feeds)
+- FIX protocol basics
+
+*** C++ Internals
+- Memory model: stack vs heap, RAII
+- Move semantics, copy elision, RVO
+- Templates and template metaprogramming
+- Undefined behavior and compiler optimizations
+- SIMD intrinsics (basics)
+- Custom memory allocators
+- Lock-free data structures: CAS, atomics, memory ordering
+- Ring buffers, lock-free queues
+
+** Track 3: System Design
+- General: scalability, load balancing, databases, caching
+- Low-latency architecture patterns
+- Co-location and proximity hosting
+- Order book design and matching engine
+- Market data feed architecture
+- Tick-to-trade pipeline design
+
+* Phased Timeline
+** Phase 1 — Foundations (Weeks 1–3)
+Goal: Build base knowledge across all three tracks simultaneously.
+
+- [ ] LeetCode: arrays, hash maps, linked lists, stacks, queues (easy problems)
+- [ ] Systems: OS fundamentals — processes, threads, memory management
+- [ ] C++: review move semantics, RAII, memory model
+- [ ] System design: read about scalability basics
+
+** Phase 2 — Core Patterns (Weeks 4–7)
+Goal: Pattern recognition in LeetCode; go deeper on low-level topics.
+
+- [ ] LeetCode: binary search, two pointers, sliding window, trees, DFS/BFS (easy–medium)
+- [ ] Systems: CPU caching, cache lines, false sharing, NUMA
+- [ ] Networking: TCP/UDP deep dive, KCP
+- [ ] C++: atomics, memory ordering, lock-free basics
+- [ ] System design: practice 1 question/week (general scalability)
+
+** Phase 3 — Advanced (Weeks 8–11)
+Goal: Finance-specific systems knowledge; harder algorithm problems.
+
+- [ ] LeetCode: heaps, graphs, DP, math/probability puzzles (medium–hard)
+- [ ] Systems: kernel bypass (DPDK, RDMA), UDP multicast, CPU pinning
+- [ ] C++: lock-free queues, ring buffers, custom allocators, SIMD
+- [ ] System design: order book design, matching engine, market data feed
+- [ ] Read about FIX protocol and tick-to-trade pipeline
+
+** Phase 4 — Mock & Polish (Weeks 12+)
+Goal: Interview simulation; fill gaps; stay sharp.
+
+- [ ] Timed LeetCode sessions (medium difficulty, 45 min each)
+- [ ] Mock system design interviews (1–2/week)
+- [ ] Review flashcards daily (Anki)
+- [ ] Company-specific prep: research each target firm's tech stack
+- [ ] Behavioral stories in STAR format
+
+* Resources
+** LeetCode Lists
+- Blind 75
+- NeetCode 150
+- Optiver / Jane Street past problem types (probability, brainteasers)
+
+** Books
+- "Computer Systems: A Programmer's Perspective" (CS:APP) — OS/memory
+- "C++ Concurrency in Action" — lock-free, atomics
+- "Designing Data-Intensive Applications" — system design
+- "Trading and Exchanges" — market microstructure
+
+** Online
+- NeetCode.io — structured LeetCode patterns
+- Martin Kleppmann's DDIA
+- "What Every Programmer Should Know About Memory" (Ulrich Drepper)
+
+* Weekly Rhythm
+| Day | Focus |
+|-----+-------|
+| Mon | LeetCode (2–3 problems) |
+| Tue | Low-level systems study |
+| Wed | LeetCode (2–3 problems) |
+| Thu | System design practice |
+| Fri | C++ deep dive |
+| Sat | Mock interview or review |
+| Sun | Anki review + weekly reflection |