SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c83f652e69540dc5fca8cdb330ceaa833b0da4b25f35b0beceac1ec5c79623c3' 
  AND token = '1tmQrQmRe7UcU2tgI2JDV3orKYMDmZQEcvvg2OFfQis=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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