SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c1b7e23562407066bc71192f60eceba2a18f717f7fec7d3dbc31f28bb544146' 
  AND token = '17uCwFdxVrU7UjHaXZ56zrLzCy8MuEWInXm4gSa3BXY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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