SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b21a98c923e8f60995645367b1e85e928d70d1e60f7a32e20595e33835323fd' 
  AND token = 'Ic6Mez+8MjAlqAYVKQwScKkLHi5v/qQObs/+rbLGYkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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