SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50987b097afa05043d31de973d571653bcaf89d2d8b825749e4f6223edb7a2f' 
  AND token = '8pm8jvC7at/hVZxr4MGipSrAjwMIIr02sVTtUxI9zKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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