SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b4d334541551ccb2cbe644f890ecd552a15f7a17f067fc2a53e11561a8cb83' 
  AND token = 'Ag7bWVBMEId3fiAYXD3nTOGuP3zzEi3/8vZLku4LoG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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