SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51e0dd9fd96ca181aae28680bea2866403b8c7a01701228cac0c29d1f352643' 
  AND token = 'KK+LErecI9L/mJRGnRN+c8o/QEYQf1OFYtjnQaHfxEA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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