feat-sdk

Server-side Ruby SDK for feat feature flags. Local flag evaluation against a polled datafile. Standard library only - no gem dependencies.

Install

# Gemfile
gem "feat-sdk"

bundle install

Ruby 3.0+.

Usage

require "feat"

client = Feat::Client.new(
  api_key: ENV.fetch("FEAT_SERVER_KEY"),
  data_plane_url: "https://data.feat.so",
)
client.start

ctx = {
  targetingKey: "user-123",
  user: { plan: "pro", email: "alice@example.com" },
}

if client.get_boolean_value("checkout-v2", false, ctx)
  # ...
end

client.close

Use a server API key (feat_sdk_...).

How it works

• Fetches a per-environment datafile and keeps it in memory.
• Polls every 30 seconds by default. ETag-aware via If-None-Match.
• Evaluation runs in-process: no per-flag network call.
• A background thread handles polling; close stops it cleanly.

License

MIT