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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c3e6670cb54e7652a17fbba166b404cb1a49eee9f77e9ac9d2f2961f1d030f31' 
  AND token = '3FSY19ZVyysuOhMojRzPJKi60gdTqvqiaNAjZip6t7c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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