SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1671b5efb35060b914ee45fa8eb5414334afd2e1e14857406f338817f790e86c' 
  AND token = 'J8mgbOZ7BOwz5NKmMK5UV8YZ4rqGWHTMig4A84zSwqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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