SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15696d2736bc2007765133ce91fb8bd1f8afee855a767b4b57931d7db6fabb41' 
  AND token = 'nZMGHaU0w9MvsgL3NPjDFdgGqY+giClL667FKvVdLOI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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