SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '842885662d4ce061606a83260c834ef342be9ef59898a261d0fc06798bf42fda' 
  AND token = 'K88dikL5Ldc7f5zx1u9UHiTwvbNIZaBvQFpYxKxJxNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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