SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2851fcf9c37b84734f2d878b661fa357f06e1c298fbee7d588d70b7240cd44d' 
  AND token = 'Pmb4HBNWJxw4ANwNbqX29lYshpgulPiXATZ3CZGaTNE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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