SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fce78938143cbc29cb48fe3ad682a336443d35d0015bb7b32f4a9f64493300f4' 
  AND token = 'zSx4XXYPqKVAYcWBBclaHnQjyG7NMqMgjfU6SImZ5RI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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