SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7ec42247e90ce67891bd2fc75d9df904f9eb4cd04c5eb422d71a6a5b94c63e21' 
  AND token = 'R24eSSOBigY3jwZiBLTZw4fxsjZ2Wiv/rAHWzQxksdk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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