SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51d10d60d9ef0056988587fa6fdd08df66e973b0b6ba54ccfb053e71c9af3bd3' 
  AND token = '5X3OKdNDLa0/DYsletISw3mw9P1HtSf0SQ7HZ7pEJTU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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