SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8d3ffe2a3a673b4eed0d7f2e9d596c91f60987a3c863e698756799355ee8ada' 
  AND token = 's+2FTOYVJpyTH8KwgwZIqSbza5jaxxrKYmJgdqpJGTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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