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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cf42468f2bc6d42b4d1b6499c63b5291a39a14942599ad7e480daaa788b86b55' 
  AND token = 'lSp4x1hHB7yEfXR+2wxQFoT78GWVdYKXYuUbJ7ie2Bc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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