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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '15cee6b1ad02cd76e43d5371b5688f24d3e371443b68c6d01c6269eab3c434ba' 
  AND token = 'XqtyAurw0+HxoFeai0HlsVEhYT7eoqSDTbDQxeQLxZM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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