The Redis storage strategy for node-letsencrypt is capable of storing and retrieving keypairs, accounts, certificates, and certificate keypairs from a Redis database. It is most useful in production setups where multiple load balancers need to provide HTTPS-based proxying for a number of application front-end systems.

It is strongly advised that any production Redis system is deployed using at least password-based authentication in addition to protections like IP-based request limiting and client-side TLS certificates. Unauthorized access to the Redis database enables an attacker to spoof any certificate stored in the database.

The following options may be set in the options parameter:

• {boolean} debug - set to true if debug output is desired.
• {integer} certExpiry - delete certificate entries from database after this many seconds, default is 100 days.
• {object} redisOptions - options passed to the Redis driver

To instantiate a Redis-based Let's Encrypt plugin:

  // configure Redis-based Let's Encrypt storage backend for storing keys and certs
  var leStore = require('le-store-redis').create({
    debug: true
    redisOptions: {
      db: 2,
      password: 'M3C1lSO1kLBdPd95tJGu1I0OtTp4c5Rz'
    }
  });

This object may then be used in the Let's Encrypt constructor.

The Redis database is designed to be scalable to at least thousands of domains. Scalability past tens of thousands of domains has not been tested, but should work (in theory) based on the indexing layout and available memory.

There are three primary types of data that are stored in the database:

• Keypairs are stored in keypair-HASH entries.
• Accounts are stored in account-HASH entries.
• Certificates are stored in cert-HASH entries.

There are five types of indexes in the database:

• idx-e2a-HASH entries store email to account mappings.
• idx-e2k-HASH entries store email to keypair mappings.
• idx-e2c-HASH entries store email to certificate mappings.
• idx-a2c-HASH entries store account to certificate mappings.
• idx-d2c-HASH entries store domain to certificate mappings.