Back-end Engineer:
https://roadmap.sh/backend

![Warning]! = iffy if i got the concepts to know correct
** = what even is this??? (unknown unknown)
* = not fully conceptualized or have actually used (known unknown)
? = i want to understand the higher/broader concepts better (deeper wisdom or rusty)

Internet:
? How does the internet work? - OSI Model, BGP Protocol, and ISPs
? What is HTTP? - TLS/SSL, Security Mechanisms, RESTFul
What is hosting? - Web Servers, Hosting Architectures
DNS and how do they work? - DNS Records, DNS Resolution
Browsers and how do they work? - DOM Constructions and Repainting, HTTP Requests

Language:
? Compilation - Linking, AST, Platform-agnostic (Bytecode), Make
Execution - Concurrency, I/O, Exceptions, Memory (how it's used)
Page-Tables, Sys Calls, CPU Caching, OO-Execution, Spec-Ex - i'm kidding...

Frameworks (they didn't have this?):
Flask - Blueprints, Templates, Decorator Extensions (Microservices)
Django - App, Models, Templates, Views (Monolithic)
Spring-boot - Models, Databases, Controllers, Repositories

Relation DBs:
(PostgreSQL, SQLite, MySQL, Oracle)
Syntax - SQL, Complex Queries, Building Queries
? Data Structures - Index Structures, Tables, Keys (mostly just the underlying algorithms)
Relationships and Forms - XNF, X-X Relationships, Complex Joins (sigh)

API General Topics:
REST APIs - Stateless, Error Handling, and OAS
Authentication - OICD, JWT, OAUTH2
* Testing - Unit, Integration, Functional

Caching:
(Redis, Memcached)
Server-side - Key-Value, Cache Invalidation
* Client-side - Cookies, CDNs

Web Security:
* Firewall - Packet Inspection & Filtering
* CORS - Headers, Preflight
* Security - OWASP, Hashing, Best Practices 

Database Grab-bag:
ORMS - Classes, Relationships, SQL as Classes
* Best Practices - ACID, no N+1, Normalization, Transactions
** Failure Modes
** Performance Profiling

Software Architecture:
Monolithic - Front End <-> Back End <-> Another Service
Microservices - Front End -> Back End or -> Another Service
Service Oriented Architecture - In between monolithic and microservices (specifically DBs)
** Serverless, Service Mesh, Twelve Factor Apps

Parts of the Roadmap Left (In-Order):
* Scaling Databases
* Design and Development Principles
* Docker (In-depth)
* Kubernetes (In-depth)
* Scaling APIs
* Monitoring
* Message Brokers
* Search Engines
* Web Servers
** Real-Time Data
* NoSQL DBs

Skipped in Mentions:
Git
Testing

To be a better Back-end Dev I need to focus on:
Scaling APIs and DBs Theory
Learning API Ecosystems (Logging, Brokers, Servers)
Using Real-time Data (non REST)
Trying NoSQL DB Solutions

--
END, *'s still need to be removed before roadmap check-off