SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51fbf985481dc3e661159ff039614943f99bd9c7e651b64c01b045f66203aeec' 
  AND token = 'fwd6LeBxNM9yonWm6fCpjUyRSr2KfuPfimxc+5cdVZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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