SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f3bd3c390ba988c4bb342a39e08597340d2f698f36a9bcbe72362092dd77a3b' 
  AND token = '3ATekWkwREnMVPoLbfySbZRFCp83rfF8bkgcgG5wsho=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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