SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '852e3a3e174346f2a254261f6fa739b15b375914ecb707c2d5d0c4fcbe024e31' 
  AND token = 'RpM07QvBb6AZKVWjHbzI27APCR4f4dUM+DOYhgvmHuU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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