SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a89393c0e77f945a17b4980aae4a61c7f459d119c866e50f312cf4f4f8195449' 
  AND token = '6nYG6kTLqlhqPQhslm6M5B+OxQzYVrMZywt0riruhpI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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