SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '393f1eace9abc4148cec992c37629f182e1d5893825f5d368290da34f60f8d8f' 
  AND token = 'CQ2g/6nCjCBcIyyTP+Ymd8pBsPIxkJccU4N3JN3vO4k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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