SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '709ddf1396cc5e0c29c2d052e2b2edc7468a249d998124fb3b188ad8c268aad6' 
  AND token = 'nKZsna4BjWlsZzbVzIpsQ7l5f25vv4hH5PeFw3BFv/8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}