SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4e6978e36b28a61017dd3e29d59f151eedc4dc8c35f5e94e1211f21ad4b9d2e' 
  AND token = 'GSsQs6bZCBqjvTsyvMIlM/7UvZvR+4G7Bz43Kj93YDk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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