SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcd553fcf4198dc99114610925bc1e43ac8c717a4528588d5182ac264cf54e03' 
  AND token = 'OxLY24euqPkIsdOITn14gO00gB2lpIeWZMR32UU+tNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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