SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3bf423b38dfeab96c5f3fc896676f44f140f84321aa1b1552370848d30857a4d' 
  AND token = '6uXsZXnwOjwns4nQCCZwYG3QvhdROV1cTetagrUova8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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