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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c3e4105ab5fcabd1c9149edbb6fc2234fdd5eb66f547e56cec3dc4a1621d7e7c' 
  AND token = 'eM+CkmgFwNWzEjoa9hd8KGBHbnQWBYFA6uFnUDj4by0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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