SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16346da0cb46553f351674939659dd102626146363fa6515fa372f63264cdd08' 
  AND token = 'CnCRf+xxpHUM69dvltupAMs6XrSfClsXA/UTlkSUFK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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