SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '953309646b2f9295b7120e56cc4463b11da31bc2da2a19061f57f01951a988d3' 
  AND token = 'C+fx8IXJs28GblNE2u1uM2S5KeNjwKupQVDz/umqe/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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