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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e9d93b36186d5b04506561e1171e5efb2b29a664c8426a215a9165af45c2d77d' 
  AND token = '5mrsPWnKpcTQoyHe2aaGrJhOYbBvfmn4tsWzad8o9+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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