SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '321a348565f1f5005ce0835714c86f709d2b9c4199bbea3d10ec2d51d2da7f06' 
  AND token = 'XwFVdUfme7sEuN9w9IZPrdGiLQtgaxgNdEP1dpsQL/8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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