Mid-level
Queues and messaging: asynchronous processing and decoupling
Don't block the request waiting: how queues and messaging decouple services, absorb load spikes and make asynchronous processing reliable.
Jun 25, 2026
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Back-end
What a back-end engineer needs to master at each stage of their career. From the first HTTP request to distributed architecture — the concepts that come up in technical interviews and in everyday work, explained directly. Filter by level below.
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Junior
How the web works: HTTP, request and response
What really happens between typing a URL and the page showing up — DNS, request, response and the cycle that underpins every back-end.
Jun 24, 2026
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Junior
REST APIs: what makes an API RESTful
Resources, verbs, status codes and statelessness — the API vocabulary every back-end uses and every interview asks about.
Jun 22, 2026
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Junior
Essential SQL: CRUD, JOIN and transactions
How to talk to a relational database: the four operations, the types of JOIN and why transactions exist (ACID without the pain).
Jun 20, 2026
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Mid-level
Authentication vs Authorization: sessions, JWT and OAuth
Who you are (authentication) and what you can do (authorization). Sessions, JWT tokens and OAuth explained without the mystery.
Jun 17, 2026
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Mid-level
The N+1 problem: how the ORM betrays you
The hidden query that multiplies database access and tanks performance — how to spot it and fix it with eager loading.
Jun 15, 2026
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Mid-level
Backend caching: when to use it and how to invalidate
Caching speeds everything up — until it becomes a source of bugs. Cache-aside, TTL and why cache invalidation is one of the hard problems in computing.
Jun 13, 2026
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Senior
Scalability: vertical, horizontal and load balancing
Grow up or grow out? Stateless, load balancers and the limits of each strategy when traffic explodes.
Jun 10, 2026
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Senior
CAP theorem and eventual consistency
Why distributed systems force you to choose between consistency and availability when the network fails — explained with examples.
Jun 8, 2026
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Senior
Resilience: idempotency, retries and circuit breaker
Failures will happen. How to design a back-end that survives them: idempotency, retry with backoff and the breaker that prevents the domino effect.
Jun 6, 2026
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Self-assessment: where are you?
Check what you already master. Your progress is saved in this browser only.
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Quiz: test what you learned
Four questions per level, with an explanation and the article that covers each topic. Ace a level and you can mark it in the self-assessment above.