SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78d48550dff993a757ef17051f8006582aeef76135e304de5550a0df630c3f82' 
  AND token = 'eIFMcQ2q2iJ/6g661tK1Zllv+UIt9b7uHnjWWwSrnw8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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