SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56f0e0679eae106281900aad47dfd0b244d2a04385420c8ca501ce98fbdc53c6' 
  AND token = '4VsSrjMB9Lm+eJ9ncXdXVKfr9PDnZg+/fiOsPt2lKA8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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