SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4c589e8d7009dd064955ad861bee255cfbf27d6af8350b40944884994f3cdb1' 
  AND token = '6hac55h5tgaL+lP1DA9+vx0zb6PyfwBEPeAWv20jZu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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