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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'df0e4f0002b911905a18828e8b62c4c57424652c09b848f8e6c719c537af31a0' 
  AND token = 'UDaSp5SDxUikBBtXrjjvZTDlMvbMZkrnUvlObmLAQ54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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