SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a6a78bd27308610c8da6f1a8c432efa75c55031fa8230abd4cfbe39e8201dd0' 
  AND token = 'pJQm6kTqKklKe8YZ2cDqS5YiGFdjw6GLd/b9FoOvTS8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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