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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8708ed80c4d455a7b6666f9c1e8dbc17856acc3552df3db288f1defdd4058ba' 
  AND token = 'Bq71PGuhbj34kiQZB/UpjYOaMyCC3XUYqkEkB1S1rAs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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