SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '210d76f711c78295de419427b004f2fd9ab638f0e5e16910f3d833bdc684ea71' 
  AND token = 'z+OUrZGgP5URVJEkqcWaW9B2LZGPRKD11w5JekGKWgQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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