SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '535273c8a6555c646817dbcbfe6515442cc91e2982acdba12bafeb547beda74b' 
  AND token = 'M5S7SU5+ohPhBdQCkAxv9CstV1J+TytjA3VUr5r+BVI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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