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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8e7f33cc5c84ea6db5540751491923b12c9b96568cff73d49046e01534f0e0ef' 
  AND token = 'jVW6VwbymBKTDxylfOrmDEZCB5Td+NW1TjbzaCrCihU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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