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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42b94abecc92ecd6f6903023e3a16a3fcc6481c5ab02bae867e8b5b544c52ec5' 
  AND token = '9Td3QAmqQ2jjtsS2cRRIyAobFqGTbkGIvfM0Hdn8A30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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