MODULE 03 / FIELD NOTES
Engineering
Field Notes
Practical write-ups on production systems, technical decisions, and the trade-offs that only appear after software meets reality.
ENGINEERING / PUBLISHED
Field Notes library
Computer Networking Fundamentals
5 notesNAT: Addresses, Ports, and Connection State
Trace packet translation and return-path state, calculate hot-destination port capacity, and design NAT egress around failure boundaries, observability, and explicit access policy.
Subnets: Address Planning and Packet Paths
Learn how subnet masks affect packet paths and how cloud and Kubernetes allocators turn address planning into a capacity problem.
IPv4 and IPv6: Packets, Paths, and Production Migration
Compare packet behavior, trace dual-stack connection choices, and plan IPv6 migration around translation, security, and failure recovery.
IP Addresses in Production: Prefixes, Routes, and Identity
Understand IP addressing through CIDR, packet forwarding, NAT, IPv6, and the failures that appear when networks grow.
OSI and TCP/IP: How Real Networks Work
Follow requests through IP, TCP, TLS, HTTP, proxies, and container networks to find the boundaries that matter in production.
System Design Fundamentals
9 notesWhy No Architecture Is Perfect
How to compare feasible designs, recognize conflicting requirements, and revise architecture decisions as workloads and risks change.
The Trade-offs Behind Every System Design
How to reason about speed, freshness, durability, scale, and complexity by following where work and state move.
How Much Does Big-O Matter in System Design?
Use asymptotic complexity to spot growth problems, then budget the I/O, fan-out, queues, and failures it cannot describe.
Capacity Estimation: From DAU to QPS, Storage, and Bandwidth
Turn user activity into traffic, data, and network budgets—then test the assumptions before buying capacity.
Stateless vs Stateful: Where Does the State Live?
Why moving state out of a server changes scaling and failure boundaries—and when keeping state close to computation is the better choice.
Vertical vs Horizontal Scaling: Where the Bottleneck Moves
A practical guide to adding capacity, finding the real bottleneck, and deciding when one larger node is simpler than many smaller ones.
Reliability and Fault Tolerance: The Recovery Path
A practical guide to failure boundaries, safe retries, replication, overload control, and proving that recovery actually works.
What Scalability Really Means
How to reason about growth, bottlenecks, load distribution, partitioning, overload, and the cost of adding capacity.
The Five Constraints of System Design
A practical mental model for latency, throughput, availability, durability, and consistency—and why improving one can make another harder.