SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a51936643f4f316751e98380aea4952f95b7f28be413187d537699379680924' 
  AND token = 'jqStThQdaoHV0itfDrkuO6iGYKE2rC71mtagIU+R3Rc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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