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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a3e7aa2cf1e366df5fb8fc74f1352895fcb39b75a09ea9c28094da786bbd6cf4' 
  AND token = 'DjXgr4STy6MutTfpKpaiQ7KrROuYVAy3mnVzw6WnCto=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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