SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdfddba7cd037acec8231d6d08a25535698e88b6844003c459483d5667694c51' 
  AND token = 'Kx6yJQ1+kbfP1ubhU6wXWFehTLamB5VBvuX+lEC4v78=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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