SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5b45b3051b3e16590441398b5d78cfdf6d958777061c81612b30026ddf9eca5' 
  AND token = 'Py+38tGxAHhKcJI4X6VCJ7TYwzTrP5w3/GWJZql4BCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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