SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18cb4b1353e172461888fd2bfd4d1fbc8819a44b71f92376567144178cca946c' 
  AND token = '42iAWAmXvRIiSsHA5oQtVRzchGGjwBJOhcawuw4i2mk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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