SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '81addf7318e0b0d57254f806431d72ec0880f59aaa8f1887ec6b876f73d2fdb2' 
  AND token = 'vr030D6Yom9dRgFspEBtfNSGsD/RTnc7mGk31Gq2nM8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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