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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c81c2c7efb9ca1fd0ee576d06bba3fa938d20dc683baaf2168cc9a24a5c26a9f' 
  AND token = 'n41o9+vFERPgShBLnXXFExGpBaK6sr0GEsxQeWQmFbY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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