SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3a4f7e652edcb0e53a0459165f6c969f60f740f38287fb6e39dde4a05ba06dc' 
  AND token = 'QfomPoFHzTpiQCXzfQLTIPBhus7XeLap6ACHRCpaGVg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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