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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b9c5c9a15cc5a23aa701c4fe110f946f9b933ce5f705b55feaa2e00f0bf20c35' 
  AND token = 'laHQr88V8Rdh8ZhviStwSw9RYahlPcKBqZ5ZfQErk+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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