The opener to a from-scratch series on building applications on top of foundation models in Go — what AI engineering actually is, how it differs from traditional ML and from ordinary software, and why Go is a serious language for the systems around the model.
The opener to a from-scratch AI-engineering-in-Go series: what AI engineering actually is, how building on foundation models differs from traditional ML and from ordinary software, and why Go is a serious language for the systems around the model.
The working mental model an AI engineer needs — next-token prediction, attention, training, and sampling — without the transformer math, and with every fact tied back to a decision you make in code.
The working mental model an AI engineer needs — next-token prediction, attention at an intuition level, pretraining vs post-training, and sampling — with every fact tied back to a concrete decision you make in code.
The unit a language model actually reads is neither a word nor a character — it is a token, and once you see the world the way the model does, half of its strange behavior stops being strange.
The unit a language model actually reads is neither a word nor a character but a token. How byte-pair encoding builds a vocabulary, why tokenization explains half of an LLM's strange behavior, and how to count tokens exactly in Go.
Make your first model call from scratch with net/http and encoding/json — the chat/messages API shape, a typed client with a Bearer key and context timeout, robust error handling, and server-sent-event streaming — no framework required.
Make your first model call from scratch with net/http and encoding/json — the chat/messages API shape, a typed client with a Bearer key and context timeout, robust error handling, and server-sent-event streaming.
From-scratch Go for the two mechanisms that turn an LLM from a text generator into a component you can wire into real software — schema-constrained JSON and function calling — both spoken over the same OpenAI-compatible chat JSON.
Getting reliable machine-readable output from an LLM in Go: structured output (json-schema mode, decode into a typed struct, validate with a bounded retry) and tool/function calling (the full round-trip loop, decoding tool arguments, returning results tied to the call id).
Treating the prompt as a real engineering artifact — grounded in how a next-token predictor actually works — with roles, specificity, few-shot examples, decomposition, chain-of-thought, grounding, temperature, injection defense, and versioned Go templates you can test.
Prompt engineering as a real engineering discipline: roles, specificity, few-shot, decomposition, chain-of-thought and its cost, grounding, and prompt injection — plus building prompts as versioned, testable Go text/template templates you treat like code.
Turn text into a `[]float32` that places meaning in space — what an embedding is, cosine similarity implemented by hand in Go, calling an OpenAI-compatible /embeddings endpoint with net/http, and a worked pairwise-similarity example that scores related sentences higher.
Turn text into a []float32 that places meaning in space — what an embedding is, cosine similarity implemented by hand in Go, calling an OpenAI-compatible /embeddings endpoint with net/http, and a worked pairwise-similarity example that scores related sentences higher.
Build a working in-memory vector store and exact k-nearest-neighbor search in Go by hand — no vector database — then understand precisely what HNSW, FAISS, and pgvector optimize when brute force finally runs out of road.
Build an in-memory vector store and exact k-NN search in Go by hand: a VectorStore with Add and Search, top-k selection with container/heap, normalize-on-insert, an honest look at when brute force is right, and when ANN (HNSW, FAISS, pgvector) earns its keep.
Wire the embedding client, vector store, and chat client from the last five posts into one working RAG pipeline in Go — ingest and chunk documents, retrieve the top matches for a question, inject them as grounded context, and generate a cited answer, all from scratch.
Assemble embeddings and vector search into a working RAG pipeline in Go: chunk documents, embed and store them, retrieve the top-k for a query, augment the prompt with grounded context (and cite sources), then generate — a baseline end-to-end Answer() built from scratch.
Why the naive RAG pipeline from post 9 underperforms in production, and the concrete, evaluation-driven fixes — structure-aware chunking, hybrid search, reranking, query transformation, and deliberate context construction — each explained with the reasoning and a real Go sketch.
Why naive RAG underperforms and the techniques that fix it: measure recall@k first, then structure-aware chunking, hybrid dense+BM25 search fused with RRF, over-retrieve-then-rerank, query transformation (HyDE, multi-query), and deliberate context construction against lost-in-the-middle.
Building a real agent loop in Go by hand — an LLM in a loop that picks tools, runs them, reads the results, and repeats until the task is done — so you can see there is no magic behind LangGraph, MAF, or ADK.
Build a minimal but real agent loop in Go by hand: an Agent with a tool registry and a reason-act Run loop, an iteration budget, validation against hallucinated tools, feeding tool errors back as observations, and parallel tool calls — the loop frameworks formalize, demystified.
Give the hand-rolled Go agent from post 11 a memory it can carry between turns and a plan it can follow across many steps — a compacting conversation buffer, retrieval over the post-8 vector store, and a plan-then-execute-then-reflect loop, all built from scratch.
Give the agent memory and planning in Go: a compacting short-term conversation buffer, long-term memory as timestamped embeddings in the vector store, and planning — plan-then-execute, reflection and re-planning when observations contradict the plan, and task decomposition.
How to know whether an LLM system actually works — building an eval dataset, the four metric families (deterministic checks, text overlap, embedding similarity, LLM-as-judge) in Go, task-specific eval for RAG and classification, and wiring a scored regression gate into CI so you measure instead of vibe.
How to know whether an LLM system works when outputs are non-deterministic: build an eval dataset, score with deterministic checks, embedding similarity, and LLM-as-judge (with its biases), evaluate RAG and classification, and gate regressions in CI.
Making an LLM system faster and cheaper without touching the weights — the levers an application engineer actually controls, from streaming and caching to token trimming, model routing, and Go's real superpower: concurrency with a rate limiter.
Make LLM systems faster and cheaper without retraining: TTFT vs throughput, exact and semantic response caching, prompt caching, token reduction, model routing and cascades, and Go concurrency with a worker pool and rate limiter.
The last post in the series: what changes when the LLM system you built across posts 1-14 has to run for real — reliability, security, cost, observability, evaluation gates, and versioning, from a Go engineer's seat, with code where it earns its place.
The capstone: running an LLM system in production from a Go engineer's seat — reliability (timeouts, retries, fallbacks), security (injection, least-privilege tools, secrets), cost and observability, CI eval gates, and versioning models and prompts.
This series is part of a larger body of work by Pratik Dhanave, an Agentic AI Architect writing about production AI systems, distributed systems, and cloud-native engineering. Explore all course series, browse every post, or find topics via the tag index.