SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39fb478874fb005b2b19f6720a6748c1770973eb9945d0f30e3566c929b050f6' 
  AND token = 'iQLizyAAhmjqT6DoS02tAYtjA5fZCUkdJUPx0kk+lnY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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