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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c42d91331914a72341714e7d8d75a1ee8052ff8efc71f343d885e7d3549156fa' 
  AND token = 'JXZzd/J50LQeGzuR1PHSkQSrJNWU/LvkUovewr1Nbmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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