SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312476cf6a8c69188abb687c036226fe423a2c47a2c6e470ea841a625c970150' 
  AND token = 'X0r+V+Fvqy4WzujRSwX4tfI7c1etugeIiujDjIaq9KY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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