SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6d7308615d92a97c39d884e59e7db10d0a0c16bc1cb5688ff29b3fc0b103863b' 
  AND token = 'VCNWSstOHKYRqydQzbrVnzz/omOnma0p02VCKeNCtj4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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