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NATS — Middle

At middle level, focus on this question:

How do subjects and wildcard subscriptions let you design flexible routing without RabbitMQ-style exchange configuration?

Prerequisite: junior.md.

Subjects: hierarchical, dot-separated strings

flowchart LR Subject["Subject: orders.us-east.created"] --> Parts["Hierarchical segments,\ndot-separated - no\nseparate 'exchange'\nconfiguration needed"]

Unlike RabbitMQ's exchange/binding model (per RabbitMQ — middle), NATS has no separate routing configuration step — publishers just publish directly to a subject string, and subscribers subscribe to subjects (or wildcard patterns) directly. Routing is entirely implicit in the subject naming convention itself.

Wildcards: * (one token) and > (rest of the subject)

await nc.subscribe("orders.*.created", cb=handle_regional_order)
# matches: orders.us-east.created, orders.eu-west.created
# does NOT match: orders.us-east.shipping.created (too many segments)

await nc.subscribe("orders.>", cb=handle_all_order_events)
# matches: orders.created, orders.us-east.created,
#          orders.us-east.shipping.created (ANY depth)
flowchart LR Star["'*' wildcard:\nmatches EXACTLY\none token"] --> StarEx["orders.*.created matches\norders.us-east.created"] Gt["'>' wildcard:\nmatches ONE OR MORE\nremaining tokens"] --> GtEx["orders.> matches ANY\nsubject starting with\n'orders.'"]

🎓 Takeaway: NATS trades RabbitMQ's explicit exchange/binding configuration for an implicit, convention-based subject hierarchy — simpler to reason about for straightforward hierarchical routing, at the cost of the more sophisticated matching (headers-based routing, for example) that RabbitMQ's exchange types provide.

Test yourself

  1. Does orders.* match orders.us-east.created? Why or why not, based on what * matches?
  2. Design a subject naming scheme for a system with events for orders, users, and inventory, each needing per-region routing.
  3. Why might NATS's implicit subject-based routing be simpler to reason about than RabbitMQ's explicit exchange/binding configuration for a straightforward hierarchical use case?

Continue to senior.md.