SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6db8920738919e645d91c358232935a553eba374e77019646e8ed3bf5790a57e' 
  AND token = 'EGbyzDgvbO/njNyEnoOpNVH9nzOKk1BFPDohavv+5lM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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