SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '542a93dbb072e9d15788820c8a05be343c104e00b71cc37828a2cf210f29eb3f' 
  AND token = 'cp7k52//E09VnJpbKWdSUVtvqqqPq2558SJSPRwa2rI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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