SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0257b6fc9bee12746882f670af89b68bec3635d314898e968966683a462c5e3' 
  AND token = 'VQtzot4Yk+bTISjgRr72xpGWzN+IB1Wtw9IwVNXYlsc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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