SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f3644860764b638b512fa644d8b74bbb5c475364a19060b13f121567c38db2b' 
  AND token = 'gfJaAk0vn0dVs+s7Epd0OOHlRB1z3G9ngtEkqYkMnZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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