Every acronym the book leans on, expanded and put in context. They are grouped by the
layer they belong to — the wire, the data store, messaging, the platform, security,
observability, and the domain — so a term is easy to find by the part of the system it
describes. Where an acronym means something specific in this book, the third column says
what, because a few of them (notably ACL) carry a different meaning here than the one you
might expect.
Protocols, APIs, and the wire
| Acronym |
Expands to |
In this book |
| API |
Application Programming Interface |
The contract a service exposes — the whole subject of the book |
| REST |
Representational State Transfer |
Resource-oriented HTTP; the public, cacheable, browser-native default |
| gRPC |
gRPC Remote Procedure Call |
Procedure-oriented, HTTP/2, protobuf binary; the internal-call default |
| RPC |
Remote Procedure Call |
Calling a typed method on another process as if it were local |
| HTTP, HTTP/1.1, HTTP/2 |
HyperText Transfer Protocol |
The /1.1 and /2 suffixes are protocol versions; gRPC requires /2 |
| TLS |
Transport Layer Security |
Encryption on the wire; an L7 router usually terminates it |
| mTLS |
mutual TLS |
Both sides present certificates — workload-to-workload identity in the mesh |
| SNI |
Server Name Indication |
The hostname an L4 balancer can route on without terminating TLS |
| TCP |
Transmission Control Protocol |
The L4 connection an L7 router rides on top of |
| JSON |
JavaScript Object Notation |
Text encoding for REST and GraphQL payloads |
| SDL |
Schema Definition Language |
GraphQL’s typed schema — its published contract |
| URL / URI |
Uniform Resource Locator / Identifier |
The address of a resource; a URI identifies, a URL also locates |
| DTO |
Data Transfer Object |
A shape passed across a boundary; sharing one is model coupling |
| BFF |
Backend for Frontend |
An API tailored to one client, often a GraphQL gateway |
| SOAP / WSDL |
Simple Object Access Protocol / Web Services Description Language |
Legacy XML RPC and its contracts, migrated away from |
| WCF |
Windows Communication Foundation |
The legacy .NET service framework replaced by minimal APIs and gRPC |
| W3C |
World Wide Web Consortium |
Owner of standards like the traceparent trace-context header |
Data and persistence
| Acronym |
Expands to |
In this book |
| DB |
Database |
A service’s private store; sharing one is the intrusive coupling anti-pattern |
| SQL |
Structured Query Language |
The query language of the relational stores (Postgres) |
| CQRS |
Command Query Responsibility Segregation |
Separate write and read models, often fed by events |
| CDC |
Change Data Capture |
Streaming a database’s changes out as events, via Debezium |
| WAL |
Write-Ahead Log |
The commit log a database tails to emit those changes |
| OLTP |
Online Transaction Processing |
The transactional workload a primary store serves |
| ORM |
Object-Relational Mapping |
Mapping rows to objects; Entity Framework on .NET, JPA on the JVM |
| EF |
Entity Framework |
The .NET ORM used in the examples |
| JPA |
Jakarta Persistence API |
The JVM persistence standard |
| PII |
Personally Identifiable Information |
Data that defines a privacy and encryption boundary |
| TTL |
Time To Live |
How long a cached entry or record stays valid before expiry |
| MSDTC |
Microsoft Distributed Transaction Coordinator |
The two-phase-commit coordinator that sagas replace across services |
| N+1 |
the N+1 query problem |
One query per row instead of one batched query — fixed with batching |
Events, messaging, and streaming
| Acronym |
Expands to |
In this book |
| DLQ |
Dead-Letter Queue |
Where a poison record goes after bounded retries, so the partition keeps moving |
| EIP |
Enterprise Integration Patterns |
The messaging-pattern vocabulary (router, translator, aggregator) |
| MSMQ |
Microsoft Message Queuing |
The legacy Windows queue replaced by Kafka |
| NATS |
a lightweight messaging system |
An alternative broker named alongside Kafka |
| Acronym |
Expands to |
In this book |
| K8s |
Kubernetes |
The numeronym (K, eight letters, s) for the orchestration platform |
| HPA |
Horizontal Pod Autoscaler |
Scales replica count on CPU or custom metrics |
| KEDA |
Kubernetes Event-Driven Autoscaling |
Scales on queue depth and other event sources, including to zero |
| CRD |
Custom Resource Definition |
How an operator (or Istio) extends the Kubernetes API |
| CNCF |
Cloud Native Computing Foundation |
Home of Kubernetes, OpenTelemetry, OpenFeature, and the rest of the stack |
| OSS |
Open-Source Software |
The whole platform is OSS — no managed-cloud lock-in |
| YAML |
YAML Ain’t Markup Language |
The configuration format for Kubernetes and Istio objects |
| LB |
Load Balancer |
An L4 or L7 component spreading traffic across pods |
| L4 / L7 |
Layer 4 / Layer 7 (OSI) |
Transport-level versus application-level routing |
| VIP |
Virtual IP |
A stable address an L4 balancer fronts a backend pool with |
| NAT |
Network Address Translation |
Why IP-hash stickiness breaks behind shared addresses |
| VPC / VPN |
Virtual Private Cloud / Network |
Network isolation boundaries referenced in passing |
| IIS |
Internet Information Services |
The Windows web host left behind in the .NET migration |
| YARP |
Yet Another Reverse Proxy |
The in-process .NET reverse proxy / gateway |
| CI |
Continuous Integration |
Where compatibility and module-boundary checks run automatically |
| SDK |
Software Development Kit |
A language’s client library, e.g. the OpenTelemetry SDK |
| DI / CDI |
Dependency Injection / Contexts and Dependency Injection |
Wiring dependencies; CDI is the Jakarta standard |
| LTS |
Long-Term Support |
A release supported for years, e.g. .NET 10 |
| PID |
Process ID |
PID 1 in a container receives SIGTERM on shutdown |
| I/O |
Input/Output |
Work the domain core delegates to adapters in hexagonal architecture |
| S3 |
Simple Storage Service |
Object storage, e.g. the target of a valet-key upload |
| DSL |
Domain-Specific Language |
A focused mini-language, e.g. a business-rule ruleset |
| DMN |
Decision Model and Notation |
A decision-table standard for business-rule routing |
| PR |
Pull Request |
The review unit a schema or contract change travels in |
Security and identity
| Acronym |
Expands to |
In this book |
| JWT |
JSON Web Token |
The signed token carrying identity and claims; lets services stay stateless |
| OIDC |
OpenID Connect |
The identity layer issuing those tokens |
| SPIFFE |
Secure Production Identity Framework For Everyone |
Workload identity the mesh binds to mTLS certificates |
| WAF |
Web Application Firewall |
An edge layer inspecting requests for attacks |
| RBAC |
Role-Based Access Control |
Authorisation by role, enforced at the gateway or in policy |
| IAM |
Identity and Access Management |
The broader identity and permission system |
| KMS |
Key Management Service |
Where encryption keys live, outside the application |
| MFA |
Multi-Factor Authentication |
A second identity factor at the edge |
| OPA |
Open Policy Agent |
The policy-as-code engine for authorisation decisions |
| AD / NTLM |
Active Directory / NT LAN Manager |
Windows identity and its legacy auth, replaced by OIDC and mTLS |
Observability and reliability
| Acronym |
Expands to |
In this book |
| OTel |
OpenTelemetry |
The vendor-neutral instrumentation standard for traces, metrics, and logs |
| OTLP |
OpenTelemetry Protocol |
The wire format from your service to the collector |
| LGTM |
Loki, Grafana, Tempo, Mimir |
The open-source backend stack for logs, dashboards, traces, and metrics |
| SLO |
Service Level Objective |
A reliability target, measured by SLIs and promised in an SLA |
| RED |
Rate, Errors, Duration |
The request-centric monitoring method |
| USE |
Utilization, Saturation, Errors |
The resource-centric monitoring method |
| RTT |
Round-Trip Time |
Network latency; what locality-aware routing minimises |
| p50 / p99 |
50th / 99th percentile |
Latency percentiles — p99 is where L7 hop overhead shows up |
| MDC |
Mapped Diagnostic Context |
Per-request fields attached to every log line, e.g. the trace id |
| SRE |
Site Reliability Engineering |
The discipline behind SLOs, error budgets, and these methods |
| ETW |
Event Tracing for Windows |
The legacy telemetry source replaced by OpenTelemetry |
Domain, architecture, and language
| Acronym |
Expands to |
In this book |
| DDD |
Domain-Driven Design |
Bounded contexts and ubiquitous language drive where API boundaries go |
| ACL |
Anticorruption Layer |
In DDD, a translation layer keeping a foreign model out of yours — not an access-control list |
| XOR |
exclusive OR |
The coupling rule “modularity = strength XOR distance” — have one, not both |
| MVC |
Model-View-Controller |
The legacy web UI pattern migrated from |
| UI |
User Interface |
The client surface, e.g. Blazor in the .NET stack |
| AI |
Artificial Intelligence |
The agent context the opening chapter frames the book around |
| RAII |
Resource Acquisition Is Initialization |
The C++ lifetime idiom tying cleanup to scope |
| JVM |
Java Virtual Machine |
The runtime for the Spring Boot and Quarkus examples |
Standards and licensing
| Acronym |
Expands to |
In this book |
| RFC |
Request for Comments |
An IETF standard, e.g. RFC 9457 Problem Details, RFC 9745 Deprecation |
| IETF |
Internet Engineering Task Force |
Publisher of the HTTP, Problem Details, and Idempotency-Key specs |
| MIT, BSD, Apache 2.0, AGPL |
open-source software licenses |
The licenses on the pinned toolkit and platform components |
Verification status: compiled from the book’s own usage — every entry appears in the
chapters or appendices. Expansions follow each technology’s canonical naming; where a term
is overloaded (ACL), the meaning used in this book is called out explicitly.