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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'da3c86e76da5713670b3662cf33df8e2738442c201801275650982df0bc02457' 
  AND token = '6z4pjMBN48rohAlYxcy4JqCrz15pae4/QfsZ5xYBLcU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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