SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e755acff712bc050df67ba122ad6883e176ffa24982d0c6e28d8e8a370bc395a' 
  AND token = 'iTHjB+i06mdnZsXKMrz2zczFF+GTFDntTJLqqbNemv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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