SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a38578ae20451c1efa3a3f63bbb06b7aaa9692f5d23af5d1adb8d10c668789c' 
  AND token = '4FZ7M6kk5BdiPw+qsUwVdza3zBRZuZXgxYq2ODcG5Nk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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