SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b84e40c608a3a4a0f00e046128180fac83bc5fe3ee40039edabc671337eed109' 
  AND token = 'H506kRNSp2JiFLv5wXAXvKWC6UMmVeH+jDmQ2Hik5iA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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