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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6c3a28a838ddbfd01ed8d71e552894d5356a5cb884dbf971ec4ba60b24a0a513' 
  AND token = 'ctBcS/wCaffjqpFR81LerzHs5aqcfh67fo8YcSqC63E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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