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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'eb37542f82a9fb608b83c38c300a759aedc15fcec2ece9029a9798ce2e2dd04f' 
  AND token = 'ST3RrTOXt4C2tpdbyuC4N2sMc8H6YLTnTCnWG4OQrwE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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