SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e31ffbfcc10331b69812120974883ccdd6f7ab531202222ec274ace17c9884' 
  AND token = 'Yg0QkivrQbxGO24Dw1i24zYM+RS2UbLnapSnwJZkIB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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