SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76c7f37417f95e4e27fcfeeec9f366dd1a5f6282047d17bc0c9398286d3b7869' 
  AND token = 'QXqHHb8YPugtZGBTQJRULhIa3LL3ZPV934ygBhbAJNY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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