SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '790cbce83436f975bb9b99597792c1e64c04114e3611736fa4b57f0313dad25a' 
  AND token = 'YzKkPg+qZt0ZTRID8CluyEDzgWGZxcaXuqitiU1LhEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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