SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1cd3642fa9a95b59d7da55e32101d5f1de870ca3d915a66503e72e1b1a66056' 
  AND token = '2YYhXbtWQBhsOwiYZkgoVVouS60wi9oZW8uN+sp7eDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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