SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '355c310f6cf2d89a8cb4df3ebb8518d55417c39851b69437a2850be460a7b61f' 
  AND token = '9EOJ1IL+hqy2k6ofOwBPEGD14mg+7sK9kXjG4crGebQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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