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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd5b5c50b2ff5c73bd4f4209d019edff45f045e46f552a39bc7b7441eb5461217' 
  AND token = 'RMr1rMXbadeE4NJmyJw9pVJrbNZhLzYZ74C39XnAglU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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