SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '644312062ed8a2bbad73b422881efc68d971431aece127c166953947a2f5e573' 
  AND token = '1ex8Hf3ssczzfGbXi6TH0r+80mQT11o+Nz7lpEOY7o8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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