SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aa137a63c9e6ab1cb6b648ad52c06959e4e29b9dc4688603e0f1dc31926ea84a' 
  AND token = 'VTvvIeq3pNkh7BxvzHKKVghI4Y8eL+IsXjhUCRjFBaA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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