SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6940748bd61d126da0c28630c749e4d48807416b6c4d8aca48a26404da91750' 
  AND token = 'TZEtA1sqSN4gSFEt6zLo+aXjIoW5wCNgR5AqFd3fyxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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