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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c309a8d79e011fe5a44f17a52c9383a20a6d5c020921f90ec2b42a90c46a6c43' 
  AND token = 'IKqMZudViVNwy/ImoUuCyc3UIwz/7WOfBTNcFLkja0E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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