SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90bb65d40d9a8b9b37206721e62fae6f2f15b15c453649d968650392aed69fe9' 
  AND token = 'iUs0FB7NnAtIywCuZov1UBys3etNTguzLR7ErlLIqNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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