SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '900c5ff46b18c1fe6e36ba22b3b1a936296a12c670458b30525b21684799e334' 
  AND token = 'z8/+M8/iEKBjJi16mloGhw9p7Bz7+boScrthBEuKfbA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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