SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '285207b884b4b7a726a20ce249bdaf18e5f7d07e9bfc07f3e6ead0af30b2b18d' 
  AND token = 'u6xzxZbTEkCvtj/+1w3Cq8Ac+GmpPvDL3UywuYJ5tM4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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