SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b576fb90e8eeb1333651f6c1ae88640d61734d45ffdf64839e6041a88c979c0' 
  AND token = 'JQPjhqh17GD2B09Im1LWhVoJ0ZQswnctKcX+Z8Bk6nM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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