SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b83c4f3f0ef0fd1f2cf553f490b85678aacca6649e032b7adf0371ab7a239ec6' 
  AND token = 'fUsmRq5QVYhpzvrqqmY7gzIl1kBNUAt6ChclIJkfONw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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